Meanwhile South Korea urged North Korea on Monday not to use the impeachment crisis in Seoul as an excuse for stalling six-nation talks on its nuclear weapons programmes.

In a sign the government wants to keep Asia's fourth-largest economy on track amid crisis, a Finance Ministry official said the government would seek a supplementary budget if necessary.

Friday's parliamentary vote stunned many, sparked nightly protests by thousands of candle-waving South Koreans and thrust the country into uncertainty.

The Constitutional Court has six months to decide whether to uphold the vote, and Prime Minister Goh Kun is acting president during that time.

The Unification Ministry said the North and South would discuss when and how to reschedule the talks, which had been due to discuss economic cooperation and transport links being built through the Demilitarised Zone border.

Venue change says North

The North wanted the talks moved from Paju in the South to Kaesong in the North.

"As the venue of talks has been suddenly relocated by North Korea, practically it was impossible to hold talks today," said a Unification ministry spokesman.

It was the first tangible fallout for North-South ties from Friday's impeachment vote amid rowdy scenes in parliament.

"If North Korea uses the impeachment as an excuse to be reluctant or to try avoiding six-party talks, we'll have to question North Korea's commitment to seeking peaceful resolution to the nuclear issue"

Ban Ki-moon, South Korean Foreign Minister

But the cancellation of Monday's economic discussions raised fears that the communist North may use the prospect of leadership change in Seoul to complicate six-nation talks aimed at dismantling Pyongyang's nuclear programmes.

"If North Korea uses the impeachment as an excuse to be reluctant or to try avoiding six-party talks, we'll have to question North Korea's commitment to seeking peaceful resolution to the nuclear issue," South Korean Foreign Minister Ban Ki-moon said.

Ban said he would dispatch his deputy, Lee Soo-hyuck, to Beijing on Tuesday to discuss convening a third-round of nuclear talks without hitches.

Last month, the United States, the two Koreas, China, Russia and Japan held a round of nuclear talks aimed at easing tensions over the North's nuclear programme, but negotiations ended without a major breakthrough. They agreed to meet again by July.

Political crisis

The political crisis began on Friday, when, in a spectacle televised live, the opposition-dominated National Assembly used security guards to drag out screaming and kicking pro-Roh lawmakers.

It then passed a bill impeaching Roh for alleged election-law violations and incompetence.

Chaos broke out during the
impeachment of Roh on Friday

The move appeared to be backfiring on the opposition, as public surveys showed the popularity of the small Uri Party, which supports the president, surging ahead of the 15 April parliamentary polls.

Tens of thousands of Roh supporters have converged on downtown Seoul every night since the impeachment to protest against the opposition.

Police said 35,000 people showed up Sunday night, chanting "nullify impeachment" as they waved candles and demanded Roh should be reinstated.

On Sunday, North Korea condemned South Korea's presidential impeachment as a US-masterminded "coup" in its first comments on the crisis.

"This is not merely an internal affair of South Korea. It is a political rebellion staged by a handful of political quacks quelling the mind-set of tens of millions of South Korean people," the North's official KCNA news agency said late on Sunday, citing a North Korean government spokesman.

North Korea's dispatch accused Washington of masterminding Roh's impeachment, saying: "It was none other than the United States that sparked such disturbing development."