(For related factbox, please click on [nSEO18306]) (Recasts with presidential spokesman)

By Jack Kim

SEOUL, March 27 (Reuters) - North Korea on Thursday expelled South Koreans from a joint factory park north of the border in retaliation for the new government's tough tone towards Pyongyang, a move Seoul warned could chill once warming ties.

The predawn expulsion of the officials at the Kaesong industrial site, once hailed as a model of economic cooperation, is one of the most aggressive moves in years by the destitute North against its wealthy neighbour that supplies it with aid.

Presidential Blue House Spokesman Lee Dong-kwan said after an emergency meeting that the North's measure "was a very regrettable incident that could damage progress of economic cooperation between the South and the North".

President Lee Myung-bak's government, in office barely a month, has pushed the touchy North to clean up its human rights record, repatriate its citizens held by the communist state and make progress on nuclear disarmament.

Spokesman Lee said North Korea needs to be more predictable in its dealing with the South, adding his government did not want the situation to deteriorate.

Park Young-ho, an expert on the North at the South's Korea Institute for National Unification, said: "You can see this move as North Korea trying to train the new South Korean government and put pressure on it."

He added Pyongyang was also looking to stir up conflict in the South over how to treat its prickly neighbour.

The North's official media has yet to report that Lee has become president, the first conservative in the job after a decade of left-of-centre leaders who handed over billions of dollars in aid to try to win over the reclusive state and maintain stability on the peninsula.

UPSETTING RELATIONS

North Korea's KCNA news agency this month quoted an official as warning that conservative elements in Seoul were upsetting relations by "letting loose malignant vituperation, slandering and defiling even the regime and system in the DPRK (North Korea)."

A Unification Ministry official said the North had told 11 South Korean officials on Monday they would have to leave the site, finally forcing them out before dawn on Thursday.

"The North cited Unification Minister Kim Ha-joong's comments that without the resolution of the nuclear problem, there won't be any expansion of the Kaesong project," the official said.

Some 23,000 North Koreans work in nearly 70 South Korean factories at the park, about 70 km (45 miles) northwest of Seoul, producing clothing, shoes, watches and other goods for salaries a fraction of those in the South.

On Wednesday in Washington, South Korean Foreign Minister Yu Myung-hwan said that major powers were losing patience with Pyongyang's failure to produce a full accounting of its nuclear weapons programme as required under a 2005 deal.

The North, which battles chronic food shortages, had asked previous governments to supply it with massive amounts of rice and fertiliser but has yet to ask Lee's government. [ID:nSEO362014].

Analysts said the North was still working out how to respond to Lee's demand that aid be linked to progress on humanitarian and nuclear issues.

North and South Korea on Thursday started without incident separate talks about energy and economic aid promised to the North in return for its pledge to eventually end operations at its ageing nuclear plant that produces weapons-grade plutonium. (Additional reporting by Lee Jiyeon) (Writing by Jon Herskovitz; Editing by Jonathan Thatcher and Alex Richardson)

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