UNITED NATIONS (NYT) - President Bush challenged the United Nations on Tuesday to put aside its sharp differences over Iraq and to help the Iraqi people build a peaceful and democratic country on a timetable that made sense to them.

But he stoutly and unapologetically defended the American rationale for the war. He suggested that the world might need to act preemptively again to prevent attacks by terrorists equipped with unconventional weapons.

Such attacks could bring "suffering on a scale we could scarcely imagine," Bush said.

Bush's somber address to the General Assembly drew a single, 20-second round of applause at its conclusion. That stood in contrast to last year, when members of the United Nations praised him for his ultimately fruitless decision to ask the organization to grant specific authority for tough action on Iraq.

Now, as a U.S.-led victory in Iraq has given way to prospects of a long and sometimes violent occupation, the United States is exploring the possibility of seeking a new Security Council resolution to open the way for greater global contributions of money and peacekeeping troops to Iraq.

"The nation of Iraq needs and desires our aid," he said, "and all nations of goodwill should step forward and provide that support."

But Bush's comments, and those shortly afterward by Prime Minister Jacques Chirac, underscored the serious gap that persists in the heart of the Security Council.

While Chirac has called for a substantial turnover of authority to Iraqis within months, Bush pointedly said that the transformation could not be "hurried, nor delayed" to satisfy the wishes of outsiders.

"This process must unfold according to the needs of Iraqis," he said.

Bush noted that he had asked Congress to authorize reconstruction spending in Iraq that will outshine that of the Marshall Plan in Europe after World War II. Now others needed to join in, he said.

He outlined the broader role he seeks for the United Nations in Iraq.

It should help Iraqis develop a constitution, train civil servants and conduct elections, he said. He has said troops there should remain under the command of the United States.

"Every young democracy needs the help of friends," Bush said.

In making his plea for international support, the president couched his comments in terms of Iraqis' needs, not of Americans' wishes.

He acknowledged the differences that have riven the United Nations over Iraq, but said that it was time for its members to join in helping establish an Iraqi democracy that he said could serve as a model for remaking the entire region.

Bush defended the rationale for the Iraq war, saying Iraqis were still being interviewed about weapons programs even though no weapons of mass destruction have been found.

If unconventional weapons reached the wrong hands, Bush said, they would pose such a devastating threat that the world could not wait to act.

Such weapons, Bush said, "could be used by terrorists to bring sudden disaster and suffering on a scale we could scarcely imagine," posing "a peril that cannot be ignored or wished away."

He said, "All words, all protests, will come too late."

Bush called on more countries to join an anti-proliferation initiative that recently mounted training exercises on the interception of weapons shipments.

Enzi, Thomas praise speech

Sens. Mike Enzi and Craig Thomas, both R-Wyo., applauded President Bush for his address to the U.N.

Thomas agreed with Bush, citing a responsibility among all nations to ensure a prosperous future for Iraq.

"The Iraqi people have regained their independence, and I thought the president did a good job stressing the importance of moving forward with Iraq reconstruction, which will help foster the country's development," he said.

Enzi commended Bush for setting the tone for the rest of the morning's speakers and encouraging an international dedication to security.

"The president reiterated our strong commitment to the people of Afghanistan and Iraq and the rebuilding of their nations," he said. "I believe democracy and stability in both of these countries will ultimately benefit the entire world."

Thomas said it was also important of Bush to reiterate his commitment to snuffing out terrorist groups that threaten the United States and its allies.

While Bush sought to move past the rancor over the war, both Chirac and Kofi Annan, the United Nations secretary general, were not prepared to do so.

Speaking before Bush, Annan denounced the American logic of preemption. Chirac said pointedly, "There is no alternative to the United Nations."

Annan said the deeply divisive debate over the war pointed to the need for a fundamental re-examination of the workings of the United Nations, above all to look at ways collective action should be used to address challenges to peace.

The logic of preemption, Annan said, "represents a fundamental challenge to the principles on which, however imperfectly, world peace and stability have rested for the last 58 years."

If adopted more generally, he said, "it could set precedents that resulted in a proliferation of the unilateral and lawless use of force, with or without justification."