WASHINGTON - US PRESIDENT Barack Obama on Tuesday welcomed South Korean President Lee Myung-Bak to the White House, sending a signal of airtight ties with Seoul as North Korea's nuclear belligerence escalates.

Mr Lee arrived for the talks after indicating that he wants the United States to offer fresh guarantees that South Korea is under the US security umbrella, days after the United Nations slapped new nuclear sanctions on Pyongyang.

OTHER THINGS ON THE AGENDA MR LEE'S visit had been planned months in advance as part of the young Obama administration's outreach to key allies. The agenda was originally expected to focus on broadening the two nations' alliance, which was borne of the 1950-53 Korean War but has expanded to include cooperation in the Vietnam, Iraq and Afghanistan conflicts and economic issues. ... more MR LEE, a conservative businessman, took over last year and delighted many in what was then George W. Bush's Washington by reversing a decade-long 'sunshine policy' under which South Korea put few restrictions on aid to the impoverished North. The latest nuclear showdown with North Korea is clouding the fate of two female US journalists jailed by Pyongyang last week for 12 years. Washington has said it considers the case of the reporters as separate from the nuclear row and has been trying to win their release. ... more

The two leaders were to spend several hours together, including a private one-on-one session, expanded talks with officials, Mr Obama's first Rose Garden press availability with a foreign leader and a working lunch. Mr Lee was then set to head to Capitol Hill for talks with the top Democratic and Republican leaders in the US Senate.

The summit comes a day after the latest show of defiance by North Korea, which said 100,000 people rallied to denounce a tightening of UN sanctions on the hardline communist state for testing a nuclear bomb.

Pyongyang sent east Asian tensions into overdrive last month with its second nuclear detonation, which followed what Washington said was a disguised test of a long-range missile in April.

Mr Obama came to office offering negotiations with reclusive North Korea, but Kim Jong-Il's government has grown ever more defiant.

On Saturday, the North vowed to build more nuclear bombs and start enriching uranium for a new atomic weapons programme, in response to the new UN sanctions.

Some analysts have speculated that the saber-rattling is primarily rooted in an attempt by ailing 67-year-old Kim to bolster a succession plan involving his youngest son, Kim Jong-Un.

Mr Lee's office said in a statement earlier that US Secretary of Defense Robert Gates had reassured him in talks Monday that Washington was committed to defend South Korea 'through all necessary means, including the nuclear umbrella.'

The United States stations some 28,500 troops in South Korea and more than 40,000 more in nearby Japan, which also has tense relations with Pyongyang. -- AFP