President’s son-in-law and adviser spoke with ambassador Sergei Kislyak at event at Washington hotel

WASHINGTON— Jared Kushner, President Donald Trump’s son-in-law and a senior White House adviser, on Monday released details of his contacts with Russian officials and businesspeople in the two years since Mr. Trump launched his presidential campaign, including a previously undisclosed meeting with the Russian ambassador to the U.S. in April 2016.

In the newly disclosed April encounter—shortly before Mr. Trump would become the Republican party’s effective nominee—Mr. Kushner met ambassador Sergei Kislyak at an event at the Mayflower Hotel in Washington, D.C. Mr. Kushner said he was introduced to Mr. Kislyak and three other ambassadors by Dimitri Simes, the publisher of a foreign-policy magazine who was hosting the event, at a reception held directly before it.

A spokesman for Mr. Kushner had previously denied that the two met privately at that event. A separate Kushner spokesman said Monday that the statement doesn’t contradict the previous denial because the two met at a reception, not one-on-one.

“The ambassadors…expressed interest in creating a positive relationship should we win the election,” Mr. Kushner wrote in his statement. “Each exchange lasted less than a minute; some gave me their business cards and invited me to lunch at their embassies. I never took them up on any of these invitations and that was the extent of the interactions.”

Mr. Trump, who gave a speech addressing foreign policy at the event, also greeted Mr. Kislyak and three other foreign ambassadors who came to a VIP reception held before the event, The Wall Street Journal reported in May 2016. Mr. Kushner’s account makes no mention of Mr. Trump being present at the reception. Attorney General Jeff Sessions also attended the event, and said in sworn testimony before a Senate panel in June that he couldn’t recall whether he had a passing encounter with Mr. Kislyak there.

To underscore the brief nature of the interaction, Mr. Kushner referenced an email he wrote on Nov. 9 after the campaign received a note of congratulations from Russian President Vladimir Putin. “What is the name of the Russian ambassador?” Mr. Kushner asked in an email to Mr. Simes, an American born in Moscow, saying he wanted to verify that the Putin note was real.

The meeting with Mr. Kislyak was revealed in an 11-page statement Mr. Kushner prepared for congressional committees probing allegations of Russian involvement in the 2016 presidential campaign. Later Monday, he is set to hold a private interview with the Senate Intelligence Committee, which will mark his first time speaking with congressional investigators.

“I had no improper contacts,” Mr. Kushner wrote in the statement. “I did not collude, nor know of anyone else in the campaign who colluded, with any foreign government.”

In the statement, Mr. Kushner also denied trying to establish any “backchannel” with Russia, though he acknowledged that in a December meeting with Mr. Kislyak, Mr. Kushner proposed receiving information about military operations in Syria via a secure communications line at the Russian embassy, because the Trump transition team had no secure system of its own.

Following Mr. Trump’s victory on Election Day, the White House repeatedly denied that there had been any contacts between his campaign and Russian officials. “It never happened,” spokeswoman Hope Hicks told the Associated Press in November. “There was no communication between the campaign and any foreign entity during the campaign.”

Since then, it has emerged that several members of Mr. Trump’s campaign—some of whom now serve in his administration—did have contact with Russians. They include Mr. Sessions, former national security adviser Mike Flynn and the president’s son, Donald Trump Jr.

Congressional investigators and Special Counsel Robert Mueller, who is overseeing a criminal probe for the Federal Bureau of Investigation, are investigating Russian meddling in the 2016 election, as well as whether Trump associates colluded in that effort.

Mr. Trump and his campaign aides have denied any collusion, and the president has said he questions the U.S. intelligence agencies’ consensus that Moscow sought to intervene during the campaign—a charge that Russian officials have denied.

The Russian Embassy announced on Twitter Saturday that Mr. Kislyak has concluded his assignment in Washington.

Russian Ambassador to the U.S. Sergei Kislyak
Russian Ambassador to the U.S. Sergei Kislyak Photo: Carolyn Kaster/Associated Press

The revelations of the Russia meetings come at a time when Congress is considering legislation imposing new sanctions on Russia as retribution for its interference in the 2016 presidential campaign.

The bill, which already passed the Senate on a rare and overwhelming bipartisan 98-2 vote will pose a test for the president, who has expressed skepticism about the intelligence community’s assessment of Moscow’s role in the campaign, from hacking Democratic emails to promoting fake news. The White House press secretary Sarah Huckabee Sanders on Sunday said Mr. Trump was likely to support the legislation.

Meanwhile, the Senate Judiciary Committee has summoned Paul Manafort, Mr. Trump’s campaign chairman for three months in 2016, and Donald Trump Jr., the president’s eldest son, to a hearing on Wednesday, along with Russia sanctions activist Bill Browder and Glenn Simpson, the founder of a political intelligence firm in Washington called Fusion GPS. Mr. Simpson, a former Wall Street Journal reporter, was subpoenaed to appear before the committee on Friday.

Mr. Simpson’s attorneys have said they are prepared to fight the subpoena. The Judiciary Committee said Donald Trump Jr. and Mr. Manafort are providing documents to the committee and are still negotiating the terms of their testimonies.

The new meeting disclosed on Monday comes on top of three previously confirmed meetings Mr. Kushner has held with Russians. He also disclosed that in October—days before the election—he reported to a Secret Service agent an email he received from someone under the name “Guccifer400” that threatened to “reveal candidate Trump’s tax returns and demanded that we send him 52 bitcoins in exchange for not publishing that information.” The agent advised Mr. Kushner to ignore the email, and Mr. Kushner said he wasn’t contacted by the sender again.

In June 2016, Mr. Kushner met with Russian lawyer Natalia Veselnitskaya, Mr. Manafort and Donald Trump Jr. in a meeting arranged by the younger Mr. Trump. Emails the president’s son released earlier this month showed the meeting was held to discuss allegedly damaging information about Democrat Hillary Clinton they were told was being offered by the Russian government in support of the elder Mr. Trump’s candidacy.

In an email to the younger Mr. Trump dated June 3, 2016, a British publicist said that a top Russian prosecutor had “offered to provide the Trump campaign with some official documents and information that would incriminate Hillary and her dealings with Russia and would be very useful to your father.”

The younger Mr. Trump responded: “[If] it’s what you say I love it.”

Mr. Kushner said Monday that he arrived late to the meeting and left early, sending his assistant an email that said: “Can u pls call me on my cell? Need excuse to get out of meeting.” He said that while he was there, the meeting didn’t discuss “anything about the campaign” and said there was no follow-up.

Mr. Kushner disclosed the meeting with Ms. Veselnitskaya earlier this year in a required form to obtain a security clearance. Mr. Kushner initially filed a disclosure that didn’t list any contacts with foreign government officials, but the next day submitted a supplemental disclosure saying that he had engaged in “numerous contacts with foreign officials.”

He said Monday that the omission of foreign contacts was an administrative error.

Mr. Kushner has since submitted information about “over 100 contacts from more than 20 countries,” he said. That information hasn’t been publicly disclosed, but Mr. Kushner said Monday the contacts included meetings with Israeli Prime Minister Benjamin Netanyahu and Luis Videgaray Caso, the secretary of foreign affairs for Mexico.

White House officials also said earlier this year that Mr. Kushner met in December with Messrs. Kislyak and Flynn. Mr. Flynn resigned in February as national security adviser after it was disclosed he misled officials about his contacts with the Russian ambassador.

During that meeting, Mr. Kushner said Monday, he asked Mr. Kislyak to “identify the best person…with whom to have direct discussions and who had contact with his president.” He also expressed a desire for a “fresh start in relations.”

Mr. Kushner subsequently had aide Avraham Berkowitz handle another meeting requested by Mr. Kislyak, during which the ambassador sought to arrange a meeting between Mr. Kushner and Sergei Gorkov, the head of Vneshekonombank, or VEB, the officials said. Mr. Kushner’s meeting with Mr. Gorkov took place in December at a location other than Trump Tower, a senior administration official said.

In 2014 the U.S. imposed sanctions on the Russian development bank, naming entities and individuals operating in Russia’s economy following Moscow’s annexation of Crimea. The Treasury Department sanctions prohibit specified financial contacts with the bank and others on the list.

The White House’s account of that December meeting has differed from that of VEB, which said its leadership met with Mr. Kushner in his capacity as the head of the real-estate firm Kushner Cos. A senior administration official said earlier this year that Mr. Kushner didn’t know the bank was under sanction and “wasn’t there to discuss business.”

On Monday, Mr. Kushner said they discussed “no specific policies” and said Mr. Gorkov “told me a little about his bank and made some statements about the Russian economy.” Mr. Gorkov also said he was “friendly with” Mr. Putin.

In his statement Monday, Mr. Kushner acknowledged that he proposed receiving information about military operations in Syria via a secure communications line at the Russian embassy, but he denied trying to establish any “backchannel” and said his interest in talking to Russia via secure means was solely to obtain information about the conflict in Syria.

The idea to have direct contacts with Russia about Syria during the transition came from Mr. Kislyak, who said at the December meeting in Trump Tower that he wanted to relay information from Russian “generals” who couldn’t come to the U.S., Mr. Kushner said.

The Wall Street Journal previously reported that Mr. Kushner had discussed with the Russian ambassador the possibility of setting up a secure communications line with Russia during the transition and using equipment at the Russian embassy, according to a person familiar with the matters.

A mode of communication like that could have made it more difficult for the U.S. intelligence agencies to intercept and listen to conversations. And two other people with knowledge of Mr. Kushner’s activities during the transition said his interest in creating what they described as a “backchannel” with Russia raised concerns among law enforcement and national security officials about his and the team’s activities.