| Lee has apologised over his government's handling of the beef trade deal with the US [GALLO/GETTY]|
Earlier in the day a 56-year-old South Korean man set himself on fire
after taking part in rallies opposing the beef deal, police said, adding that
the man was in critical condition.
Protests broke out after Lee's government signed a controversial accord on April 18 to resume importing US beef.
US beef had been banned from South Korea since the first case of mad cow disease in the US was discovered in late 2003.
Scientists believe the disease spreads when farmers feed cattle meat and bones from infected animals.
Lee, the former mayor of Seoul, scored the biggest landslide win in South Korean presidential elections history just six months ago but his approval rating has plunged to about 20 per cent.
And his Grand National party (GNP) suffered a bruising defeat in local by-elections on Wednesday – a sharp turnaround from parliamentary elections in April which saw the GNP secure a convincing majority.
|Protesters are demanding the beef |
deal be scrapped [EPA]
Lee's reputation as the "bulldozer" is also taking a beating in the economics field.
His plan to boost South Korea's economic growth has been hit by sharp increases in global energy and food prices, Lee Chung-min, a professor of international relations at Yonsei University in Seoul, told Al Jazeera.
Lee has "hit rock bottom and he has no choice but to go up", he said.
"He has to totally reconfigure his team, his policies and his strategy."
The deal to resume US beef imports has come under fire amid widespread public perceptions that it fails to offer sufficient protection from possible mad cow disease by allowing imports of beef from older cattle, considered at greater risk of the brain-wasting illness.
The government announced this week that it had asked the US to refrain from exporting any beef from cattle above 30 months old, but it stopped short of asking for a full renegotiation of the deal.
The opposition denounced that arrangement as a diversionary ploy to calm public anger and said it would accept nothing less than the scrapping of the current deal and the renegotiation of a new one.
Last month, Lee made a public apology over the government's handling of the sensitive import deal.
The president's office has said that Lee would begin meetings with religious, political and academic leaders this weekend "to seek their opinions on how to resolve the ongoing political crisis".
Source: Al Jazeera and agencies