North Korea vowed Friday to bolster its atomic arsenal in response to what it called Washington's "hostile" policy, even as a special envoy for President Barack Obama traveled to the region in a bid to draw Pyongyang back to nuclear negotiations.

Envoy Stephen Bosworth, in Beijing before heading Friday to South Korea, said the U.S. is ready and willing to talk directly with Pyongyang.

"The United States reiterates its desire to engage both multilaterally and bilaterally with North Korea," Bosworth told reporters after holding talks with senior Chinese officials Thursday. "We believe very strongly that the solution to the tensions and problems of the area now lies in dialogue and negotiation."

But North Korea dismissed the Obama administration's stance as "unchanged" from a previous policy of hostility toward Pyongyang.

"Nothing would be expected from the U.S., which remains unchanged in its hostility toward its dialogue partner," the North's Foreign Ministry said in a statement carried by state media. The North "will bolster its nuclear deterrent as it has already clarified," it said.

Pyongyang in recent weeks has taken a series of steps flouting its pledge to disarm, quitting international nuclear talks, expelling inspectors and threatening to conduct nuclear and long-range missile tests. The North also claimed it had restarted its Yongbyon nuclear facilities to harvest weapons-grade plutonium.

The statement Friday cited Washington's denunciation of North Korea's April 5 rocket launch and support for a U.N. Security Council censure as evidence of the Obama administration's hostility. The statement further noted joint military drills between the U.S. and South Korea.

Secretary of State Hillary Rodham Clinton said earlier that Washington's goal is to get North Korea back into the disarmament process, but warned that it would be a difficult job.

"We may have to show some patience before that is achieved," she told reporters after talks with Russian Foreign Minister Sergey Lavrov, whose trip to Pyongyang last month produced little progress in efforts to get the North back to the negotiating table.

Under a 2007 deal, North Korea agreed to disable its main nuclear complex in Yongbyon north of Pyongyang in return for 1 million tons of fuel oil and other concessions.

In June, Pyongyang blew up the cooling tower there in a dramatic show of its commitment to denuclearization.

But disablement came to halt a month later as Pyongyang wrangled with Washington over how to verify its past atomic activities. The latest round of talks in December failed to push the process forward.