WASHINGTON - Top U.S. and South Korean trade officials will meet in Columbia, Maryland, on Tuesday and Wednesday to try again to resolve differences blocking U.S. approval of a free trade agreement, U.S. officials said.

It will be the first meeting between U.S. Trade Representative Ron Kirk and South Korean Trade Minister Kim Jong-hoon since the two sides failed at the Group of 20 summit last month in Seoul to meet a self-imposed deadline for reaching a deal on outstanding beef and auto trade concerns, Reuters reported.

Both sides have said they remain optimistic of resolving the issues, which mainly involve U.S. auto industry complaints about tax and regulatory barriers that they say thwart sales of American cars in South Korea.

President Barack Obama's administration also is believed to want to change the terms of car and truck tariff concessions the United States made to South Korea, so that they would be phased out more slowly than both sides agreed in 2007.

Some lawmakers and beef groups also want Seoul to commit to a process to remove remaining barriers to U.S. beef exports, consistent with international food safety guidelines.

South Korea has been adamant its remaining beef import restrictions, which stem from the discovery of the first case of mad cow disease in the U.S. herd in 2003, are not up for negotiation. Seoul has also indicated it wants new concessions from the United States to offset any changes that it agrees to make to the auto provisions of the pact.

The two allies' renewed effort on the trade deal comes one week after a North Korean military strike on a South Korean island has raised tensions on the peninsula the two countries share to their highest in at least two decades.

U.S. and South Korean warships, in a show of unity and force, held military exercises on Monday, prompting concern from China and threats of all-out war from North Korea.