South Korean President Lee Myung-Bak expressed regret Thursday for his government's handling of a US beef import deal which sparked street protests by tens of thousands of people.

"I should have paid attention to what people want," said Lee, battling a political crisis sparked by the agreement in April to resume the imports.

"I and my government will acutely reflect on this," he said in a nationally televised statement.

US and South Korean negotiators are meeting in Washington to try to revise the pact and secure extra safeguards against any danger of mad cow disease.

Seoul wants the US government to guarantee a voluntary agreement by US exporters not to export older cattle, seen as potentially more at risk of the disease.

Lee said his government will secure a "firm" US government guarantee to ban beef from cattle older than 30 months.

The president, who is struggling to restore public trust in his four-month old administration, also promised to abandon a key election pledge to build a cross-country canal if most people oppose it.