President Bush is in Singapore as part of a trip that will also take him to Indonesia and a Pacific-rim summit in Vietnam. His talks in Singapore are likely to focus on trade.

Singapore is an economic powerhouse in Asia. It is also a key ally of the United States.

This will be Mr. Bush's second visit to this island-state. In addition to his talks with Singapore's leaders, he will also deliver a speech that aides say will set the tone for the entire trip.

They say he will speak about the ways Asian countries and the United States can work together to meet mutual challenges such as poverty, disease, terrorism and energy security.

His visit here, with its focus on business and trade, is a prelude to this weekend's Asian Pacific Economic Cooperation summit in Hanoi. Traditionally, these summits have focused matters like trade and development. But terrorism and North Korea's nuclear program are also expected to figure high on the agenda.

Mr. Bush is likely to continue those discussions in a series of bilateral meetings with other summit participants. They will include conversations with all four of the countries involved with the United States in the so-called six-party talks with North Korea.

Among them is Russian President Vladimir Putin. He was on hand to greet Mr. Bush when Air Force One made a refueling stop Wednesday at a Moscow airport.

It is highly unusual for the presidential jet to refuel in Russia while traveling to East Asia. And White House officials insist this was nothing more than a social visit between the two leaders.

But the brief stop in Moscow gave them an opportunity to go through the summit agenda and talk about areas of mutual concern before arriving in Hanoi. Among the topics are Iran, the situation in the Middle East and Russia's bid to join the World Trade Organization.