The president's office did not comment, but Mr Lee said on Tuesday that he would stick to his reform agenda once the elections were over, including cleaning up bureaucracy and cutting taxes, and the poll results were not expected to derail those plans.

The opposition Democratic Party won seven of 16 major races for the country's largest cities and the provinces in an upset that surprised GNP and analysts who had been expecting a large win for the conservative ruling party.

Voting for nearly 4,000 mayors, governors and local government representatives has been overshadowed by the March sinking of the RoK naval corvette Cheonan.

The RoK and the United States are to hold a naval military exercise next week, about a month ahead of schedule.