Just hours after President Obama weighed in on the potentially flawed Iranian elections, he is forced to turn his attention to another nuclear problem.
South Korean President Lee Myung-bak is scheduled to meet with the president to discuss the country's troubled neighbor to the North.
North Korea's pledge to expand its nuclear programs gives their meeting Tuesday at the White House a sense of urgency. The presidents probably will express their refusal to accept the North as a nuclear weapons state and condemn recent missile and nuclear tests.
"We cannot stress enough the importance of diplomacy at a time when a security crisis is intensifying due to North Korea's nuclear and missile threats," President Lee Myung-bak said in a radio speech before his departure Monday.
"In particular, the South Korea-U.S. diplomacy is key to that diplomacy," he said. "I will use this summit to reconfirm the strong Korea-U.S. alliance."
Before leaving Seoul, Lee said he supported Obama's appeal for a world without nuclear weapons. However, he told The Wall Street Journal, "we are faced with North Korea trying to become a nuclear power, and this really is a question we must deal with now."
The United States, during Lee's visit, is likely to pledge its continued commitment to use its military muscle to protect the South should the North attack. Such comments are welcome in Seoul and Tokyo, no matter how many times U.S. officials repeat them.
Lee's talks with Obama come on the second day of a three-day visit also scheduled to include meetings with U.S. trade envoy Ron Kirk, Defense Secretary Robert Gates and Treasury Secretary Timothy Geithner. Secretary of State Hillary Rodham Clinton welcomed Lee to Washington on Monday, the same day tens of thousands rallied in Pyongyang to condemn sanctions imposed by the United Nations after the country's latest nuclear test.
Lee's office released a statement saying Clinton had called for close cooperation between South Korea, the U.S. and Japan in implementing the U.N. sanctions to "get North Korea to realize that its bad behavior will bring due consequences."
Lee told Clinton that "as long as the United States and its allies maintain a firm stance, North Korea's belief that it will be rewarded for its bad behavior if it waits long enough will dissipate," the statement said.
North Korea is reportedly readying a possible test of a missile that could reach Alaska. The North also may be preparing for a third nuclear test in defiance of the U.N. sanctions.
The U.S. government officially confirmed Monday that North Korea carried out an underground atomic test in late May. The Americans said the blast was somewhat larger than the country's first test, conducted in 2006.
Victor Cha, a senior Asia adviser in President George W. Bush's administration, said another nuclear test could motivate U.N. member states to actually enforce the sanctions specified in the U.N. resolution against the North.
Lee has infuriated North Korea since he took office in early 2008. He ended a decade of liberal rule in which South Korea sought to embrace the North and refrained from criticism, a so-called "sunshine" policy that provided aid without demanding concessions. Pyongyang regularly calls Lee a traitor.
While the nuclear standoff will top discussions, another tense issue looms for Lee and Obama: an ambitious South Korean-U.S. free trade agreement to slash tariffs on goods and services.
The deal was painstakingly negotiated but currently is in limbo, stalled over U.S. lawmakers' worries it could hurt an already suffering American auto industry.
The agreement signed in 2007 has been promoted as a potential $10 billion boon to the U.S. economy. Failure, supporters say, would threaten U.S. standing in an important region.
Obama, however, has said the deal does not adequately deal with an imbalance that has heavily favored South Korean automakers. His administration is now reviewing the deal.