Opening up the beef market is a key precondition for US legislative approval of a separate sweeping free trade pact. Opponents, however, say Seoul has not secured enough safeguards against the dangers of mad cow disease.

Seoul agreed last month to lift the ban, on the eve of a Washington summit between Presidents Lee Myung-Bak and George W. Bush.

Seoul and Washington insist that US beef is totally safe to eat. Newspapers on Tuesday said Internet scare campaigns, and a recent TV programme, were fuelling irrational fears.

'The public frenzy over fears of mad cow disease does not seem to be dying down easily,' said the JoongAng Ilbo in an editorial headlined 'Mad cow madness.'

It added: 'Internet rumours and political instigations have stirred up public sentiment to the point where there is no room for scientific truth or reasonable explanations.'

An estimated 10,000 people on Friday staged a city centre candelit protest rally against US beef imports, and about 7,500 on Saturday. Civic groups were planning another evening protest on Tuesday even though police have said that only a 'non-political' rally will be allowed.

Parliament is to hold a hearing on Wednesday on the beef import deal.

The main opposition party's parliamentary leader on Tuesday reiterated his resolve to overturn the deal.

'At the hearing tomorrow, the UDP will disclose the truth about...the hasty and humiliating negotiations,' Mr Kim Hyo-Suk of the liberal United Democratic Party told parliament.

The UDP, he said, 'will seek to adopt a parliament resolution calling for renegotiations.'

The wider free trade agreement (FTA) was signed last year but needs ratification by both the US and South Korean legislatures. The Seoul government is seeking approval this month, to press the US Congress also to move quickly.

Mr Kim also reiterated his party's position to delay ratification of the FTA until there are sufficient countermeasures to help local beef farmers.

In response to the row, the state quarantine office said it would send inspectors to check sanitary standards at 31 US slaughterhouses. But the agriculture ministry said it would resume inspections of shipments this month, so they can be cleared for sale.

South Korea banned all US beef in 2003 due to mad cow concerns.

It eased the ban in 2006 but allowed only meat from cattle aged 30 months or less, and excluded bones and other materials deemed to carry a risk of spreading the disease.

Most of those restrictions were eased in April.

South Korea was once the third largest market for US beef, with imports worth US$850 million (S$1.2 billion) a year before the ban in 2003.

Seoul sees the free trade deal as the most significant event in relations with the US since a military accord in 1954.

Total trade is worth an annual US$80 billion and some studies show this could eventually rise by up to US$20 billion under a free trade regime. -- AFP