SEOUL -- A day after showing American delegates its "nuclear deterrent," North Korea marked the anniversary yeterday of its expulsion of United Nations weapons inspectors by resolving to bolster its self-defence against a possible U.S. nuclear attack. Yet as the isolated North kept up its typically harsh anti-American rhetoric, North Korea's official KCNA news agency also urged Washington to accept Pyongyang's offer of a freeze on its program as a first step toward resolving the crisis over its atomic weapons programs.

The American delegates arrived in Seoul yesterday after a visit to the North in which officials reportedly showed them recently reprocessed plutonium -- the fuel for atomic bombs -- to convey the extent of development and what might be curbed if the programs were suspended. The five delegates were the first outside visitors to the Yongbyon nuclear plant since Pyongyang expelled the UN inspectors.

International and domestic pressure is mounting on Washington to accept the North's offer of a freeze as a compromise to rekindle six-country talks on the nuclear standoff.

While previously rejecting such offers, the United States -- against the backdrop of the delegation's visit -- called Pyongyang's latest proposal a "positive step forward."

South Korea hailed the plan as creating "atmosphere" for new negotiations.

Meanwhile, Russia and China were working to broker a compromise that reportedly calls for a freeze as a first step toward resuming talks.

Chinese diplomats are expected to float such a proposal next week in Washington, according to Russia's Itar-Tass news agency.

The American delegation has said it was shown everything it asked to see at North Korea's Yongbyon nuclear facility, but delegates would not give details until they had briefed superiors.

One delegate, Jack Pritchard, has urged Washington to "pocket" Pyongyang's offer of a freeze before North Korea is able to strengthen its nuclear arsenal.