The U.S. military sent two long-range B-2 stealth bombers over the Pacific this weekend, according to a statement from U.S. Strategic Command. The move comes during heightened tensions between the U.S. and North Korea over the country’s rapidly developing missile and nuclear weapons programs.

The bombers which are capable of carrying nuclear payloads took off from Whiteman Air Force Base in Missouri. The military did not say where in the Pacific the bombers flew. 

The goal of the mission was to “familiarize aircrew with air bases and operations in different geographic combatant commands, enabling them to maintain a high state of readiness and proficiency,” according to the military’s statement.

U.S. Defense Secretary James Mattis was in South Korea Saturday and warned of North Korea’s growing threat to the world.

“North Korea has accelerated the threat that it poses to its neighbors and the world through its illegal and unnecessary missile and nuclear weapons programs,” said Mattis. “[The U.S.] does not accept a nuclear North Korea.”

North Korea has showcased its rapidly advancing nuclear and missile programs through a number of provocative tests this year. Last month, North Korea tested what it claims was a hydrogen bomb in its sixth and largest nuclear weapon test. North Korea has also threatened to test fire missiles near Guam, shot two missiles directly over Japan and tested two intercontinental ballistic missiles with a theoretical range of the continental U.S.

Mattis visited the demilitarized zone Friday, it's the border that separates North and South Korea.

The bomber mission also comes ahead of President Donald Trump’s visit to Asia later this week. Trump will fly to Hawaii Friday then kick off the tour five-country tour by heading to Japan Sunday.

The U.S. has used its jets on several missions as a stated show of force toward North Korea recently.

Last month the U.S. along with South Korea and Japan undertook joint bombing mission exercises in which live bombs were dropped on a test site in South Korea. Earlier in October, the U.S. flew two bombers along the Korean peninsula.