Washington, Dec 4 (DPA) The US and South Korea Friday reached a tentative deal on a long-stalled free-trade agreement, according to the top US trade official.

US Trade Representative Ron Kirk and Korean Minister for Trade Kim Jong-hoon had worked out their differences during a meeting in the US state of Maryland and were ready for the two country's leaders to sign off on the deal.

"We've made substantial progress in our discussions. It's time now for the leaders to review this progress before we move forward," Kirk said in a brief statement.

The US-South Korean pact was first negotiated under former president George W. Bush but was never ratified by the US Congress.

President Barack Obama re-opened talks when he came into office, looking for more concessions on US exports of beef and cars into the Asian power. But negotiators failed to meet a goal of agreeing to a new deal by the time of Obama's visit to South Korea last month.

US business groups have been clamouring for the two sides to resolve their differences and Friday welcomed news that a deal had been struck.

But there were already signs that the pact could face resistance within Obama's own left-leaning Democratic Party, which has typically been more skeptical of the benefits of free trade.

Congressman Mike Michaud, a leading Democrat on trade issues, said the deal did not seem to meet concerns beyond beef and cars. Michaud in a statement said he would "do whatever I can to defeat it".