SEOUL, South Korea — President Obama met today with South Korean President Lee Myung-bak, calling for North Korea to take "serious steps" to give up its nuclear weapons and committing himself to reviving a free-trade deal between Seoul and Washington stalled in the U.S. Congress.

In a nationally televised joint news conference, Lee said the two leaders agreed to offer North Korea a "grand bargain" designed to provide the North with security guarantees and economic assistance in exchange for dismantling its core nuclear programs.

The last stop on Obama's weeklong Asia tour was expected to be a bit of a diplomatic breather after the sticky foreign policy issues he faced during stops in Japan and China.

On the eve of Obama's visit, during which he also met with U.S. troops stationed here, South Korea announced the expansion of its presence in Afghanistan, saying it will send more troops and contractors to aid the U.S. effort there.

Standing on red-carpeted steps at Seoul's Blue House before colorful military regiments and waving children, Obama called the welcome the most spectacular ceremony he's enjoyed so far in Asia.

Still, serious issues loomed, most critically the ongoing efforts to bring North Korea back to six-party talks. Obama reiterated his plan to hold direct talks with the North in an effort to restart the multilateral talks that also include South Korea, China, Japan and Russia.

Obama also expressed impatience with Iran, saying he and U.S. allies are developing sanctions to level against the country if it fails to accept a proposal curbing its nuclear program.

Obama also said American and South Korean officials were working to overcome obstacles that remained in the way of a free-trade pact.