The United States proposed on Wednesday that North Korea (search) agree to a series of nuclear disarmament measures over a three-month period in exchange for economic benefits and an easing of its diplomatic isolation.

The proposal, unveiled at the start of six-nation talks in China, would ultimately lead to the end of North Korea's nuclear program.

It was the most detailed U.S. proposal for bringing about a diplomatic solution to the North Korea nuclear impasse since it surfaced almost two years ago.

The United States considers North Korea to be a threat to peace and stability in Northeast Asia. North Korea has sold missiles to countries such as Iran (search) and Syria (search), and the possibility of exports of nuclear weapons technology is a major concern here.

The United States is being joined at the Beijing talks by China, South Korea, Japan and Russia in addition to North Korea itself. The American delegation is headed by Assistant Secretary of State James Kelly. Talks resumed Thursday morning in Beijing (search).

During the three-month "preparatory period," North Korea would disable its nuclear weapons and remove key weapons ingredients.

"The permanent and verifiable dismantlement and removal of North Korea's nuclear programs would follow," State Department spokesman Richard Boucher said.

During the initial period, the nations in the Beijing talks would be willing "to ease the political and economic isolation of North Korea," according to the U.S. proposal.

Outside assistance would focus on deliveries of fuel, particularly from South Korea.

No lasting benefits would be provided to North Korea until after the disarmament had been completed, Boucher said. There would be no American assistance until the later stages of the process.

A North Korean response to the proposal was expected on Thursday, said a senior administration official, asking not to be identified.

In the meantime, North Korean Vice Foreign Minister Kim Gye Gwan offered an alternative, promising to freeze operations at its main nuclear complex, Japan's Kyodo news agency reported, citing officials at the conference. The freeze would allow for inspections.

Kim said Pyongyang has been developing nuclear weapons for protection from possible U.S. attack.

"If the United States gives up its hostile policy toward us ... we are prepared to give up in a transparent way all plans related to nuclear weapons," he said.

Under the U.S. proposal, some form of security guarantees also would be offered to give North Korea the confidence that disarmament would not trigger an attack.

North Korea long ago agreed in principle to give up its existing weapons. But it has refused to accept a U.S. claim that it has two nuclear programs, not just the plutonium-based project that it has acknowledged.

The administration says the danger posed by the North Koreans would remain if they removed the plutonium program while leaving intact a uranium bomb program that Washington contends it has.

The three-day meeting in Beijing is the third gathering of its kind and the first since February. The first two rounds yielded little progress.

All along, the United States has demanded the complete, verifiable and irreversible dismantling of the North's program.

The senior official described the U.S. proposal as a repackaging of the government's previous stance, mostly to make it more appealing to partners pushing for a more flexible American approach.

White House spokesman Scott McClellan cited Libya's disarmament earlier this year as an example that the United States would like North Korea to follow.

North Korea is believed to have two nuclear weapons and the capability to produce several more. Its missile program offers a weapons delivery vehicle.