"We hear voices calling for us to retreat from the world and close our doors to its opportunities," he said in a speech at the National University of Singapore. "These are the old temptations of isolationism and protectionism, and America must reject them."

Asserting that the spread of weapons of mass destruction to terrorists is "the greatest danger in our world today," Bush has the standoff over North Korea's nuclear weapons program atop the agenda in most of the meetings on his eight-day Asian trip. He urged allies to stand firm against a nuclear-armed North Korea — which he called "the most immediate threat of proliferation" in the region — and enforce U.N. sanctions against the country for test-firing a nuclear bomb last month.

"The transfer of nuclear weapons or material by North Korea to states or non-state entities would be considered a grave threat to the United States, and we would hold North Korea fully accountable for the consequences of such action," Bush said. "It is vital that the nations of this region send a message to North Korea that the proliferation of nuclear technology to hostile regimes or terrorist networks will not be tolerated."

With China's influence on the rise and his own stature weakened at home by last week's defeat of his Republican Party, Bush also sought to ease any doubt about the United States' long-term commitment to the region. He reassured nervous Asian allies that the United States will remain a reliable partner in liberalizing trade, confronting the spread of dangerous weapons and fighting terrorism, poverty and disease.

"Amid this new century we see threats like terrorism and proliferation and disease that have the potential to undermine our prosperity and put our futures in doubt," he said. "We must maintain our presence in the Pacific. We must seize on our common opportunities. We must be willing to confront our common threats and we must help our partners build more hopeful societies in this vital part of the world."

Bush appealed to nations across the Asia-Pacific region to salvage long-stalled global trade talks. At the same time, he pushed the idea of a free-trade agreement for the entire region — 21 economies along the Pacific Rim.

The president emphasized the United States' six decades of cooperation with Asia in helping alleviate poverty, providing security with military forces and promoting the advance of freedoms. He said the United States and Asian allies should focus future partnerships on combatting AIDS and bird flu, addressing corruption and developing next-generation energy technologies.

Bush chose this East-West crossroads with a turbulent past but booming present as the stage for the major speech of the trip. A tightly controlled city-state with a significant Muslim population but moderate values, Singapore is considered one of Washington's best friends in the region, a stalwart help in anti-terror and nonproliferation efforts and an active trade partner.

"America's presence in the Far East is very important for our own country," Bush said after a meeting earlier in the day with Prime Minister Lee Hsien Loong. He also had paid a courtesy call on acting President J.Y. Pillay and lauded Singapore's success at integrating its many ethnicities and religions by visiting its Asian Civilisations Museum.

Lee, who often has advised Bush on how to improve the U.S. image, particularly in the Muslim world, seemed pleased with the president's focus. "Singapore is very happy that America has a stake in the region," he said.

But analysts said Bush had much to prove, arriving in Asia as a lame-duck president after midterm elections even he called "a thumpin"' and amid a push by China for greater global influence.

"The level of attractiveness of China throughout Asia really cannot be underestimated," said Kurt Campbell, a top Pentagon official in the Clinton administration now with the Center for Strategic and International Studies in Washington. "I think one of the purposes of American diplomacy is to reassure friends in Southeast Asia that of course the United States still has enough bandwidth in its foreign policy and national security apparatus to focus on these issues."

For that reason, Bush was trying with his speech and throughout the trip to demonstrate that the relationship is not just about anti-terror cooperation and nonproliferation concerns, said Derek Mitchell, a former Asia adviser at the Pentagon also now with CSIS.

"The United States hasn't been there so much," he said. "China has eaten America's lunch."

Bush's national security adviser, Stephen Hadley, hinted at Washington's concern about China's ascendance as a regional power player. He said one of Bush's aims was to reassure a corner of the world undergoing change and uncertainty "as a result of the changing power dynamics within Asia."

The United States has a long list of complaints against China, including human rights, a currency Washington says is undervalued, a massive trade deficit and energy deals with countries the U.S. considers tyrannical. But Bush also needs — and gets, at least to some degree — Beijing's aggressive involvement in nuclear showdowns with North Korea and Iran.