Air Force One landed Tuesday evening at a military airport near the South Korean capital, Seoul. Mr. Bush's official schedule starts Wednesday, when he will meet for the third time with the conservative, pro-American president, Lee Myung-bak. Lee took office in February with promises to patch up relations with Washington that became strained under Seoul's previous decade of liberal governments.
Mr. Bush calls Lee a friend, which is good considering the raft of sensitive topics they will tackle Wednesday before the American president heads to Thailand, then to the Beijing Olympics.
At the top of the list is getting North Korea to live up to its commitment to dismantle its nuclear weapons program.
Sunday is the earliest that Washington could move to strike North Korea from a list of state-sponsors of terrorism, a long-held demand from Pyongyang. But first, Washington wants the North to agree to procedures for verifying a declaration of its nuclear programs that Pyongyang submitted to the international arms talks - six months late and with fewer details than the U.S. originally demanded.
Washington has called for North Korea to allow thorough inspections and interviews with nuclear scientists, but Pyongyang has so far not accepted the proposal.
"We're at a very critical moment now for the North Korean government to make a decision as to whether or not they're going to verify what they said they would do," Mr. Bush said in an interview with China's state-run CCTV last week. "It's one thing to say it, but I think it's going to be very important for them to understand that we expect them to show us."
Grateful for South Korea's troop contribution in Iraq, Mr. Bush also will try to persuade Lee to make a bigger contribution in Afghanistan to help deal with the Taliban's resurgence.
"Obviously we'd like to see a greater role for South Koreans in Afghanistan, if the South Korean people are willing to move in that direction," Dennis Wilder, the National Security Council's senior director for Asian affairs, told reporters on Air Force One.
Also on the agenda will be efforts by both presidents to have their legislatures approve a free trade agreement, with estimates it could increase bilateral trade by 25 percent. But with free trade deals with Colombia and Panama stalled in Congress, the prospects for ratification by the end of the year are unlikely.
Mr. Bush will meet with U.S. troops based in South Korea, as he did during a stopover in Alaska, where he expressed gratitude for their role in fighting terrorism.
"About a year ago, people thought Iraq was lost and hopeless," Mr. Bush said at Eielson Air Force Base, where he posed for photos with airmen and soldiers and worked the crowd, at one point lifting a baby in the air. "People were saying, 'Let's get out of there, it doesn't matter to our national security.'
"Iraq has changed - a lot - thanks to the bravery of people in this hangar and the bravery of troops all across our country. The terrorists (are) on the run. The terrorists will be denied a safe haven, and freedom is on the march. And as a result, our children are more likely to grow up in a peaceful world."
The timing of Mr. Bush's visit to Seoul is a bit better than it would have been just a few weeks ago. Public unrest over U.S. beef imports has receded, and the U.S. has reversed course on a decision that angered South Korea regarding disputed islets between Japan and South Korea.
The coalition that organized earlier protests predicted it would gather 10,000 people for another candlelight vigil in central Seoul demanding that the beef deal be renegotiated yet again. However, as of Tuesday evening fewer than 100 people had gathered at the site of the planned demonstration.
Police said some 30,000 people convened on the grassy plaza in front of Seoul City Hall for a Christian prayer service. Large South Korean and U.S. flags were held aloft by balloons overhead along with a banner reading, "Welcome President Bush."
Some 18,300 police were on high alert with riot gear and bomb-sniffing dogs to maintain order during the American president's less-than-24-hour visit to the country, the National Police Agency said.
In public opinion surveys, South Koreans remain generally positive about the United States, which helped repel North Korea in the 1950-53 Korean war and still deploys some 28,500 troops on the Korean peninsula to deter an attack.
About a million South Koreans visit the U.S. every year, and Seoul is seeking visa-free travel for them.