protests in Seoul.

The angry mobs have seriously embarrassed new South Korean president, Lee Myung-bak, and put his pro-business reform agenda which includes tax cuts and privatisation of State firms in jeopardy.

President Lee's recent decision to re-open the doors to US beef, banned after an outbreak of mad cow disease in America in 2003, have triggered widespread grievances against his government.

"The wise thing to do would be to use a method that has the same effect (as renegotiations) without damaging South Korea's international credibility," Trade Minister, Kim Jong-hoon, told a news conference.

South Korea will seek "substantive and effective" measures that would prevent imports of US beef from cattle older than 30 months, he said.

Lee's government doesn't want to alienate the US Congress to protect its push for a bilateral free trade deal between the two countries.

It is hoping importers and US exporters will adopt a "voluntary" agreement that means older beef - seen as having a higher risk of carrying mad cow disease - is kept out of South Korea.