About 2,000 protestors marched some three kilometers (two miles) along the street in downtown Jongro district, chanting slogans and carrying banners.

"US, Leave Iraq," read one banner. "Don't make young Koreans murderers," another said.

Washington has requested an unspecified number of South Korean combat troops, but sources here say the figure could be anywhere between 3,000 and

South Korea sent 675 non-combatants, including army engineers and medics, to Iraq in May, in a decision which sparked street protests and denunciation from North Korea's official media.

The protestors said in a statement that the US-led war on Iraq is a war of invasion which is banned under the South Korean constitution.

"No matter how the government may attempt to justify the dispatch of troops to Iraq, (South Korea) would be unable to avoid being named as an accomplice of the United States in the invasion into Iraq," the statement said.

It accused the South Korean government of seeking to trade the dispatch of combat troops to Iraq for a softer US stance toward North Korea in the stand-off over Pyongyang's nuclear drive.

"Sending combat troops to a dirty war in expectation for some return would only show the moral decay of the South Korean government," it said.

In comments to South Korean journalists on Wednesday, President Roh Moo-Hyun said instability on the Korean peninsula caused by the crisis would also have to be considered when discussing the deployment of troops.

"Isn't it difficult for us to accept the dispatch of our troops abroad under the unpredictable situation caused by North Korea's nuclear problem?" Roh said.

"So we need something predictable to guarantee stability on the Korean peninsula, and the key is how North Korea and the United States engage in six-party talks."

However, South Korea's Unification Minister Jeong Se-Hyun, responsible for handling North Korean issues, suggested the link to the nuclear crisis was tenuous.

South Korean Foreign Affairs and Trade Minister Yoon Young-kwan said Friday in New York that the United States was working on a more detailed plan to address the security concerns of North Korea to coax the Stalinist state into a fresh round of talks, Yonhap news agency said.

Two rounds of nuclear talks in Beijing, in April and August, ended inconclusively as Washington set the scrapping of North Korean nuclear programmes as a precondition for further negotiations while Pyongyang insisted on the United States providing a security guarantee.

"The US now seems to be working on a more detailed plan for these issues, including North Korea's security concerns," Yoon was quoted as saying at a luncheon meeting hosted by the Asia Society and the Council on Foreign Relations.

"This greatly enhances the prospects for a diplomatic resolution of the North Korean nuclear issue," Yoon said.

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