In an effort to show force, the United States flew two supersonic B-1B bombers over the Korean peninsula Sunday after North Korea said it tested an intercontinental ballistic missile (ICBM) just a few days earlier, U.S. and south Korean Air Forces said, Reuters reported.

The flight was a direct response to the missile test, as well as the previous test on July 3, according to a U.S. statement. The bombers took off from the U.S. air base in Guam.

“North Korea remains the most urgent threat to regional stability,” Pacific Air Forces commander General Terrence J. O’Shaughnessy said in the statement, according to Reuters. “If called upon, we are ready to respond with rapid, lethal, and overwhelming force at a time and place of our choosing.”

North Korea’s launch of the ICBM was personally supervised by their leader King Jong Un and was broadcasted on the country’s state television. North Korea’s official KCNA news agency said the launch was a “stern warning” to the U.S.

China is North Korea’s main ally and has disapproved of North Korea’s missile tests in the past, but in a statement Saturday China’s foreign ministry said, “At the same time, China hopes all parties act with caution, to prevent tensions from continuing to escalate,” Reuters reported.

President Donald Trump has previously expressed on Twitter that the U.S. and China are working together against North Korea, tweeting in April, “Why would I call China a currency manipulator when they are working with us on the North Korean problem? We will see what happens!.”