HANOVER (Germany) • American President Barack Obama has dismissed North Korea's offer to halt nuclear tests if the United States suspends its annual military exercises with South Korea.

He said that the US will not back down from strengthening its military alliances and defences against North Korea until the country "shows seriousness" towards eliminating nuclear weapons from the Korean peninsula.

"If North Korea shows seriousness in denuclearising the Korean peninsula, then we will be ready to engage in serious conversations with them to reduce tensions," Mr Obama said on Sunday.

He was speaking at a news conference with German Chancellor Angela Merkel in Hanover, Germany, the final stop of a three-nation international tour.

North Korean Foreign Minister Ri Su Yong told the Associated Press on Sunday that the country was willing to halt its nuclear tests if the US suspended its annual joint military exercises with South Korea.

He also said in the interview that international sanctions will not change the behaviour of the regime. "If we continue on this path of confrontation, it will lead to very catastrophic results, not only for the two countries but for the entire world as well.

"It is really crucial for the US government to withdraw its hostile policy against (North Korea) and, as an expression of this, stop the military exercises, war exercises, in the Korean peninsula. Then we will respond likewise."

Pyongyang made exactly the same offer in January last year. It was flatly rejected by the US as an "inappropriate" effort to link nuclear testing with regular military exercises.

The US and South Korea this year intensified the annual military exercises, which are expected to continue through the month, after North Korea conducted its fourth nuclear test in January.

Approximately 300,000 South Korean troops and 17,000 US troops are participating in the drills, according to the joint US and South Korean military command.

In the latest in a string of provocations, North Korea last Saturday test-fired a submarine-launched ballistic missile (SLBM).

Commenting on the test-firing, Mr Obama said: "Although more often than not (the North Koreans) fail in many of these tests, they gain knowledge each time they engage in these tests. We take it very seriously and so do our allies and so does the entire world."

He also urged China to increase pressure on North Korea.

The United Nations Security Council said last Saturday's SLBM launch marked a serious violation of UN resolutions aimed at curbing the North's nuclear drive, and urged Pyongyang to refrain from any further provocations.

Experts have suggested that North Korea's previous SLBM tests were conducted from a submerged platform.

Following its fourth nuclear test in January and the launch of a long-range rocket the next month, North Korea said it had miniaturised a nuclear warhead to be mounted on ballistic missiles and successfully simulated a re-entry test of a ballistic missile.

There are growing concerns that Pyongyang is building up to a fifth nuclear test ahead of a key political gathering early next month.

BLOOMBERG, AGENCE FRANCE-PRESSE