A B-2 Spirit stealth bomber flies over Europe in this undated Air Force photo. Angered by the recent deployment of B-2 bombers to Guam, North Korea has accused the U.S. of preparing for a surprise nuclear attack in connection with upcoming military exercises, and promised to retaliate.

SEOUL, South Korea — Angered by the deployment of B-2 bombers to Guam, North Korea accused Washington of preparing for a surprise nuclear attack in connection with upcoming U.S.-South Korea military exercises, and promised to retaliate.

The U.S. sent three of its most advanced nuclear-capable bombers to Andersen Air Force Base on Tuesday, about a week after the North test-fired a ballistic missile that flew about 620 miles before landing near Japan’s territorial waters.

North Korea’s state-run Korean Central News Agency pointed to the timing of the deployment ahead of the joint exercises expected to begin Aug. 22. American officials say the annual exercises are routine and defense-oriented.

“What should not be overlooked is that the massive forward-deployment of nuclear war hardware is underway with the approach of the Ulchi Freedom Guardian, a joint nuclear war exercise to be staged by the U.S. imperialists and the puppet forces,” KCNA said Wednesday.

“They are now mulling creating an opportunity of surprise nuclear attack in the course of the Ulchi Freedom Guardian,” it added, promising a “merciless retaliatory counteraction against them.”

“A pre-emptive nuclear attack is not a monopoly of the U.S.” it said.

The U.S. said the stealth aircraft, which flew from Whiteman Air Force Base, Mo., would participate in local and regional training exercises to prepare crews for future assignments and demonstrate a high state of readiness.

“Our strategic bomber force routinely operates around the globe and with our regional allies and partners, and this deployment is one such demonstration of the U.S. commitment to supporting global and regional security,” said Adm. Cecil D. Haney, head of the U.S. Strategic Command.

Pyongyang frequently issues statements objecting to U.S. military moves and joint U.S.-South Korean military exercises, which it considers practice for invasion. The rhetoric has been increasingly heated this year amid rising tensions since the North conducted its fourth nuclear test in January, followed by a series of rocket and missile launches.

Leader Kim Jong Un has insisted he will continue with the program despite international condemnation and toughened U.N. sanctions.

gamel.kim@stripes.com