North Korea fired dozens of artillery shells onto a South Korean island on November 23, 2010, killing two soldiers [AFP]

The US defence chief has held out the possibility that six-party talks involving North Korea could resume, but only if the reclusive dictatorship ceases its "dangerous provocations" and takes "concrete steps" to show it is serious about negotiations.

Tensions on the Korean Peninsula have been high since late November, when the South staged military drills near the countries' sea border, firing artillery into the coastal waters, and North Korea responding by shelling the small island of Yeonpyeong. Two South Korean marines died, while 15 troops and three civilians were injured.

In remarks on Friday at the South Korean defence ministry in Seoul, Robert Gates, the US defence secretary, said: "With regards to next steps on North Korea, diplomatic engagement is possible, starting with direct engagement between the [North Korea] and the South.

But the North must first meet its "international obligations", he said.

'Under attack'

Kim Kwan-jin, the South Korean defence minister, told Gates that his country feels under attack and that "many expect North Korea to conduct more provocation this year".

Earlier on Friday, in Tokyo, Gates sought to dampen fears that North Korean aggression is on the rise. He said North Korea's ability to launch a ground invasion of South Korea is "much degraded from even a decade ago".

But efforts by Kim Jong-il, the leader of the government, to procure nuclear weapons "threaten not just the peninsula, but the Pacific Rim and international stability", Gates said.

Gates also struck an ambivalent tone on China. He said that the US military presence in the Pacific is essential to restrain China, one of the world's biggest economic powerhouses, but also spoke of improving military relationships between the two countries.

China and the US still disagree about "freedom of navigation", Gates said, referring to the US view that it has a right to sail through waters that China views as restricted.

The relationship between China's military and political establishments can also be worrying, Gates said.

Sometimes, as when China this week tested its J-20 Stealth fighter, it seems the military does not inform the country's senior political leadership.

President Hu Jintao did not seem to know the test had taken place until Gates asked about it, Gates said.

"[But] in the larger sense of who controls the Chinese military and who has the ultimate authority there is no doubt in my mind that it is President Hu Jintao and the senior civilian leadership of that country," he said.