The top U.S. trade official Thursday linked the fate of a long-stalled U.S.-South Korean free trade agreement to Seoul's willingness to open its automobile market to American car makers, The Associated Press reported.

U.S. Trade Representative Ron Kirk told the U.S.-Korea Business Council in a speech that the ambitious trade deal could lead to American exports to South Korea rising by as much as $11 billion a year.

He said, however, that negotiators must deal ``with the legacy of Korea's long-closed market, especially with respect to autos,'' according to AP.

``Our market is open to Korean autos,'' Kirk said. ``All we are asking for is for our own auto companies to be able to compete on a level playing field in the Korean market.''

The two countries signed an accord in 2007 to slash tariffs and other barriers to trade, but the deal has since languished and has yet to be ratified by lawmakers.

A big worry in the U.S. Congress has been about South Korea's large surpluses in auto trade, especially as American auto companies suffer financially.

South Korea, one of Asia's leading economies, has said the deal stands, even as the Obama administration conducts a review of the Bush administration agreement.

Kirk said trade officials are developing proposals that deal with U.S. worries about auto trade. ``We believe that a level field is possible and within reach,'' Kirk said.

South Korea and the U.S. posted $84.8 billion in bilateral trade in 2008, making Washington South Korea's fourth-biggest trading partner after China, the European Union and Japan.