Two B-1B bombers out of Guam flew in the vicinity of the Korean Peninsula late Wednesday, Hawaii time, again rattling North Korea in what has become an increasing show of force in response to the North’s nuclear weapons program.

The pair of B-1Bs transited south of Korea and west of Japan to meet with Japanese fighters, the Hawaii-based Pacific Air Forces said Thursday. The Lancer bombers then flew over South Korea and linked up with South Korean fighters over the Yellow Sea.

North Korea particularly dislikes the flights of B-1B bombers from Guam to the vicinity of the Korean Peninsula, which it sees as practice for nuclear attack on the North. In the past it has threatened to test launch ballistic missiles near Guam.

“The gangster-like U.S. imperialists are ceaselessly resorting to their frantic nuclear threat and blackmail to stifle the DPRK with nukes at any cost,” said KCNA, the state news agency of North Korea. “On Thursday (Korea time) they let a formation of B-1B nuclear strategic bombers stationed at the Andersen Air Force Base on Guam stealthily fly into South Korea again to stage a surprise nuclear strike drill targeting the DPRK.”

DPRK is the acronym for the Democratic People’s Republic of Korea, the North’s official name.

The bomber flights come as President Donald Trump embarks on his first Asia trip, and amid speculation that North Korea will soon conduct another nuclear or ballistic missile test. Trump is expected to be in Japan on Sunday, in South Korea on Tuesday and in Beijing on Wednesday.

Three U.S. aircraft carriers — the Ronald Reagan, Theodore Roosevelt and Nimitz — and their strike groups are in the Asia-Pacific region and plan to hold a rare joint exercise in mid-November, the Japan Times reported.

Marine Corps Gen. Joe Dunford, chairman of the Joint Chiefs of Staff, met Sunday at U.S. Pacific Command headquarters on Oahu with senior military leaders of the United States, Japan and South Korea for talks on the North Korean threat.

“If we do have to respond (to North Korea) militarily, Japan is a critical platform from which the United States is going to meet its alliance commitments to (South) Korea,” Dunford said. “We have more than 50,000 forces in Japan. It is a platform from which we project power in a South Korean response. So the military relationship between South Korea and Japan is very important.”

The B-1B Lancer, which would be used in any strikes on North Korea and has had the most visible role in U.S. responses to the North’s missile and nuclear tests, carries the largest conventional payload of both guided and unguided weapons in the Air Force bomber inventory.

Despite North Korea’s claims, the United States eliminated the nuclear mission for the B-1 in 1994, the Air Force said. “Even though the Air Force expended no further funding to maintain nuclear capabilities, the B-1 was still considered a heavy bomber equipped for nuclear armament until 2007,” the service said.

The conversion to conventional capability began in November 2007 under the original Strategic Arms Reduction Treaty and was completed in March 2011, the Air Force said.

Two B-1Bs conducted a flyover Oct. 21 at the 2017 Seoul International Aerospace and Defense Exhibition at Seoul Airport. On Oct. 10, U.S., Japanese and South Korean forces “sharpened their combat skills” when two B-1Bs flew in the vicinity of the Sea of Japan east of North Korea and conducted night training with fighter jets from the other two nations, Pacific Air Forces said.

Sept. 23 saw B-1Bs with U.S. F-15C fighter escorts from Okinawa, Japan, conduct training over waters east of North Korea in what was, at the time, the farthest north of the South Korean Demilitarized Zone that any U.S. fighter or bomber aircraft had flown in the 21st century, according to the Pentagon.

Two B-1Bs flew across South Korea on Sept. 17 with South Korean fighters and released live weapons at the Pilsung Range in response to North Korea’s launch of an intermediate-range ballistic missile over Japan on Sept. 14, the Air Force said. B-1Bs also flew with Japanese F-15s in the vicinity of the East China Sea on Sept. 9.