WASHINGTON -- In an unusually speedy legislative process, both chambers of the U.S. Congress on Wednesday approved a free trade pact with South Korea which will apparently help broaden the scope of the alliance.

The move is expected to give a jolt to an effort by South Korea's ruling party to ratify the accord within this month over resistance from liberal opposition parties.

The Senate's 83-15 vote came on the eve of South Korean President Lee Myung-bak's summit with his American counterpart Barack Obama in Washington and a speech in a joint session of the Senate and the House. Lee arrived here Tuesday for a state visit.

Hours earlier, the Republican-controlled House also passed the implementing bills on free trade agreements (FTAs) with South Korea, Colombia and Panama.

Congress will soon send the bills to Obama for his signature.

Obama, eager to expand exports and create jobs, submitted the FTAs to Congress on Oct. 3, seeking to complete the long-overdue ratification process.

The key related committees of the two chambers _ the House Ways and Means Committee and the Senate Finance Committee _ were quick in sending them to the floor.

The South Korean leader stressed the economic gains from the FTA.

"If businesses in the two countries make active efforts, trade between the two countries is expected to increase by more than 50 percent by 2015 and sharply expand investment," Lee said in a speech at a meeting with American business leaders hosted by the U.S. Chamber of Commerce. Last year's bilateral trade totaled $90 million.

The White House also reiterated the importance of the accord and Lee's trip.

"This establishment of a new economic partnership will create jobs and economic growth here in the U.S. as well as in Korea,"

Press Secretary Jay Carney said at a press briefing. "This is a very important and significant state visit. It comes at a time that's really a high point in the bilateral relationship and in our alliance with South Korea."

The two sides launched free trade talks in 2006 and struck a deal a year later.

The administrations of Lee and Obama had additional negotiations on the accord, signed by their predecessors, in 2010 and reached a supplementary deal on the new terms of auto trade.

Obama has openly expressed hope for South Koreans to drive more American vehicles.

The U.S. FTA with South Korea is the largest trade deal since the U.S. agreed to the North American Free Trade Agreement (NAFTA) in the early 1990s.

South Korean officials expect the country's parliament to follow suit in the near future so that the trade pact can go into effect as early as in January.

Experts hailed the U.S. passage of the FTAs as a rare bipartisan achievement and one of the major accomplishments of Lee's visit.

"In terms of the economic agenda per se, I think the free trade agreement was the main accomplishment, as it was clearly accelerated to try to get it through both houses of Congress before the president's visit," Edward Alden, a researcher at Council on Foreign Relations said. "This was one potential deadline."

Richard Bush, senior analyst at the Brookings Institution, said it may be also Obama's biggest achievement in the remainder of his current term.

"Given how few political agreements are possible in Washington these days, this may be the biggest achievement in the last two years of President Obama's current term, particularly if there is stalemate in the budget negotiations," he said.