An Air Force RC-135 jet.

(CNN)A U.S. Air Force RC-135 reconnaissance aircraft flying Tuesday in international airspace over the East China Sea was intercepted in an “unsafe manner” by a Chinese J-10 fighter jet, several defense officials tell CNN.

The Chinese jet was never closer than 100 feet to the U.S. aircraft, but it flew with a “high rate of speed as it closed in” on the U.S. aircraft, one official said. Because of that high speed, and the fact it was flying at the same altitude as the U.S. plane, the intercept is defined as unsafe.
The officials did not know if the U.S. plane took any evasive action to avoid the Chinese aircraft or at what point the J-10 broke away. It is also not yet clear if the U.S. will diplomatically protest the incident.
Officials said the RC-135 was on a routine mission.
The Chinese Embassy did not immediately respond to a request for comment.
News of the intercept comes as Secretary of State John Kerry and Treasury Secretary Jack Lew are in Beijing for the annual U.S.-China Strategic and Economic Dialogue. Lew is pressing China to lower barriers to foreign business and cut excess steel production, with limited success.
A Chinese produced J-10 fighter jet is displayed outside the offices of the Aviation Industry Corporation of China in Beijing on November 28, 2013.

The intercept also occurred just days after Defense Secretary Ash Carter and top military officials returned from a regional security meeting in Singapore. At a press conference during that meeting, Carter said the U.S. would not be deterred from maintaining a military presence in the region reiterating “America’s determination to, and resolve to, fly, sail, or operate wherever international law allows.”
During that same press conference, Adm. Harry Harris, the head of U.S. Pacific Command, said military relations with China were improving.
“We’ve seen positive behavior the last several months with China. Every now and then you’ll have a — you’ll see an incident in the air that we may judge to be unsafe. Those are really, over the course of time, rare,” Harris said.
Harris said China and the U.S. both will participate in a major upcoming military exercise.
But this latest intercept comes on the heels of another intercept by China last month.
In that encounter at least two Chinese J-11 tactical aircraft carried out an “unsafe” intercept of a U.S. EP-3 reconnaissance aircraft that was conducting a routine mission in international airspace over the South China Sea, according to U.S. officials. The Chinese jets came within 50 feet of the U.S. aircraft at one point during that incident.
At the time, Beijing said the U.S. EP-3 reconnaissance aircraft flew close to China’s island province of Hainan and China’s jets “kept a safe distance throughout, without taking any dangerous actions.”
“It needs to be pointed out that American aircraft have constantly entered China’s coastal waters conducting reconnaissance, which has posed a serious threat to China’s maritime and air safety,” Hong Lei, Ministry of Foreign Affairs spokesman, said.