SINGAPORE (AP) – From across the world, President Bush took on anti-war and anti-free trade Democrats who won control of Congress, saying Thursday any drift toward isolationism would hinder America’s security and economic vitality.

“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,” Mr. Bush has the standoff over North Korea’s nuclear weapons program atop the agenda for 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,” Mr. 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 in midterm elections, Mr. Bush also sought to ease any doubt about America’s long-term commitment to the region. He reassured nervous Asian allies that America will remain a reliable partner in liberalizing trade, confronting the spread of dangerous weapons and fighting terrorism, poverty and disease.

“We must maintain our presence in the Pacific,” he said. “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.”

The president’s challenge to Democrats was clear but indirect. It came days after the House failed to pass legislation to normalize trade relations with Vietnam, a surprising setback before Mr. Bush’s trip that was seen as a troubling sign for the future of his free-trade agenda once Democrats assume power.

Previously, most debate about the impact of the Democratic takeover had focused on the Iraq war. Democrats were victorious in last week’s elections largely because of promises to press Bush to change course in the increasingly unpopular mission.

But Mr. Bush showed no sign of letting up on his desire to liberalize trade across the world. He appealed for nations to salvage long-stalled global trade talks, and pushed the idea of a free-trade agreement for 21 economies along the Pacific Rim.

With another foreign-policy priority pending on Capitol Hill – a civilian nuclear pact with India – Mr. Bush also spoke by telephone Thursday with Prime Minister Singh. The agreement has been approved by the House, and Mr. Bush told Mr. Singh that Republican Senate leaders have assured him they would act soon, said Gordon Johndroe, a national security spokesman for Mr. Bush.

In his speech, the president emphasized America’s six decades of cooperation with Asia. Future partnership should focus on combatting AIDS and bird flu, addressing corruption and developing next-generation energy technologies, he said.

Mr. 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 efforts and an active trade partner.

“America’s presence in the Far East is very important for our own country,” Mr. 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.

Mr. Lee, who often has advised Mr. Bush on how to improve the American 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 Mr. Bush had much to prove, arriving in Asia as a lame-duck president after an election result 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, Mr. 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.”

Mr. 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.”

America 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 Mr. Bush also needs – and gets, at least to some degree – Beijing’s aggressive involvement in nuclear showdowns with North Korea and Iran.