Obama, South Korea's Lee hail ties on state visit

South Korean President Lee Myung-Bak attended state dinner on Thursday during a four-day visit to the United States.

Standing side-by-side, with their close friendship on show, the leaders also spoke with "one voice" on North Korea, warning the Stalinist state faced even deeper isolation if it continued provocations and its nuclear program.

Obama welcomed Lee to the White House with trumpets and military honors hours after Congress endorsed a bilateral free trade pact signed during the Bush administration but held up by politics and market access wrangles.

"It's a win for both our countries," Obama said, arguing the deal would boost American exports by up to $11 billion and support 70,000 US jobs.

Under severe political pressure as the US recovery stutters and with unemployment at 9.1 per cent, Obama said the deal would help US automakers and open Korean agricultural, aerospace and electronics markets.

Using the same script, Lee also described the deal as "a win for both of our countries" billing the deal as a "historic achievement" that would further cement the 60-year alliance between Seoul and Washington.

He said he was confident the pact would also be ratified by South Korea's parliament in the "near future."

The leaders did not break new ground on North Korea, but their firm friendship, and the similarity of their language, reflected an apparently watertight US-South Korean stance towards Pyongyang.

"Together we've succeeded in changing the equation with the North, by showing that its provocations will be met not with rewards but with even stronger sanctions and isolation," Obama said.

"If Pyongyang continues to ignore its international obligations, it will invite even more pressure and isolation," he said, but promised more opportunity if North Korea abandoned its quest for nuclear weapons.

Lee said after private Oval Office talks with Obama and an expanded meeting with delegations, that on North Korea, the two governments "speak with one voice and we will continue to speak with one voice."

High tensions flared last year when Seoul accused the North of torpedoing one of its warships, killing 46 people, and last November the North bombarded a frontier island further enflaming ties with the south.

But last month, the two Koreas held a second round of talks designed to pave the way for a resumption of six-nation talks on the North's nuclear program and US and North Korean officials met in New York in late July.

Another meeting is expected soon, though it is not clear if either side believes tangible process is possible, or fear they need to mitigate a possible new round of provocations from Kim Jong-Il's hermit regime.

Lee also touched on North Korea in an address to a joint session of Congress, saying the six party talks also including Russia, the North, Japan and China were the best way to forge "tangible" progress.

"We are in full agreement that we must also pursue dialogue with North Korea. However, we must also maintain our principled approach," Lee said, according to a copy of his prepared remarks.

Later Lee arrived back at the White House for a state dinner for around 200 guests in the ceremonial East Room, which was decorated in fall colors.

Obama and his wife Michelle, wearing a purple off-the-shoulder gown greeted Lee and his wife Kim Yoon-Ok, wearing a traditional Korean Hanbok gown, under the North Portico of the presidential mansion.

Guests included UN Secretary General Ban Ki-moon, Facebook Chief Operating Officer Sheryl Sandberg, tennis great Billie Jean King, and LPGA golfer Christina Kim, as well as top officials and business leaders.

Lee's visit was meant to honor one of Obama's closest friendships on the world stage and one of America's most functional foreign relationships, and further anchor his policy of making Asia the key to future US prosperity.

Obama eschews chummy banter with foreign leaders, but has made no secret of the personal connection he has forged with Lee and often mentions his guest's education policies during campaign speeches.

Lee and Obama will travel together on Friday to a Michigan General Motors plant to highlight the trade pact, which ironically was once hung up on the issue of auto imports.