China (search) has pledged to try and revive talks aimed at ending North Korea's (search) nuclear programs, after the isolated, Stalinist state's declaration that it had atomic weapons and was boycotting disarmament negotiations.

The United States and other countries involved in the six-party talks have called on China to use its influence over North Korea. Beijing is Pyongyang's last major ally and a key supplier of food and energy to the impoverished dictatorship.

Foreign Minister Li Zhaoxing spoke Saturday night by phone with Secretary of State Condoleezza Rice (search) and said Beijing stands firm in supporting a nuclear-free Korean Peninsula, the Chinese government said Sunday.

Li told Rice that "China will stay in touch with all relevant parties ... so that the six-party talks could be resumed as soon as possible," the Foreign Ministry said. The discussions also involve South Korea, Russia and Japan.

South Korea's foreign minister also said he had discussed with U.S. officials "views that China should strengthen efforts to persuade the North," according to a report by South Korea's Yonhap news agency. Ban Ki-moon is in Washington on a previously scheduled trip and was to meet Rice on Monday.

North Korea announced Thursday that it has built nuclear weapons to defend itself from an alleged threat of invasion by the United States — dramatically raising tensions in the two-year nuclear standoff. Washington denies it intends to attack. North Korea's claim could not be independently verified.

North Korea also said it would stay away from the six-nation negotiations. A North Korean diplomat has reportedly requested direct talks with Washington as a way out of the impasse.

But the White House rejects such a move and insists that the North participate in the six-party discussions. Three rounds of negotiations have been held in Beijing without any breakthroughs.

On Sunday, a North Korean district official in Pyongyang said the withdrawal of U.S. troops from the Korean Peninsula would help six-party talks. Han Song Nam, a deputy chairman for a district in Pyongyang of the country's communist party, said it "would be a practical measure in the withdrawal of the United States' hostile policy," according to Yonhap, which monitored North Korea's Radio Pyongyang.

Washington has been South Korea's key security ally since the 1950-53 Korean war, and keeps thousands of troops based there and neighboring Japan.

North Korea didn't say how many nuclear warheads it had in its Thursday statement, but Australian Foreign Minister Alexander Downer said Sunday that his country suspected it had two or three atomic bombs.

Downer also warned that North Korea's declaration that it had atomic weapons could spur nuclear proliferation in Asia.

"There will be some people in South Korea, some people in Japan who will say, 'Well, if North Korea has nuclear weapons and can threaten us, why shouldn't we have nuclear weapons as well?"' Downer told Australia's Nine Network television.

Still, Downer added that he was encouraged by discussions Friday with North Korea's ambassador to Australia that talks could continue when diplomatic circumstances improved.

Meanwhile, Ban said the South had no plans to halt aid to the North, noting it provides its longtime rival with fertilizer and rice because of "humanitarian concerns." He also dismissed an American newspaper report that Vice President Dick Cheney asked Seoul to stop providing fertilizer aid.

Ban also said the South planned to push ahead with a joint industrial park just north of the inter-Korean border, if the situation doesn't deteriorate further.

The North has also repeatedly accused South Korean warships of crossing the countries' disputed sea border in recent weeks.

The allegations appear to be "in relation to North Korea's declaration that it has nuclear weapons," South Korea's Joint Chiefs of Staff said in comments reported by Yonhap.

"We believe it is part of its scheme to create military tension so that the world's eyes are focused on the Korean Peninsula," the South's military command said.