WASHINGTON - At a tense moment in his presidency, George W. Bush braced the nation last night for a looming war against Iraq and vowed in coming days to deliver new evidence to the United Nations that Saddam Hussein is concealing deadly weapons and has links to terrorist groups.

In a solemn hourlong State of the Union address, Bush accused Hussein of showing "utter contempt" toward U.N. weapons inspectors, deceiving them and blocking their work. Bush said his administration would call on the United Nations next week to review Hussein's "defiance of the world." But he already sounded like a wartime leader, telling U.S. forces massing in the Persian Gulf region that "some crucial hours may lie ahead."

The president said Secretary of State Colin L. Powell would furnish new evidence of the threat posed by Iraq, something Americans and foreign leaders have been asking the administration to do for months. Bush seemed to preview some of that evidence last night, but did not go much beyond accusations he has made in the past, saying that Hussein "aids and protects terrorists, including members of al-Qaida."

"He could provide one of his hidden weapons to terrorists or help them develop their own," Bush said. "It would take just one vial, one canister, one crate slipped into this country to bring a day of horror like none we have ever known. We will do everything in our power to make sure that day never comes."

The president spoke on a night of historic significance, with the United States on the verge of attacking another country, without decisive support from either the American public or the rest of the world. Bush made clear that he is prepared, if necessary, to order an attack without substantial international support.

"The course of this nation does not depend on the decisions of others," he said. "Whatever action is required, whenever action is necessary, I will defend the freedom and security of the American people."

Bush, whose public approval ratings have dropped steadily from once-lofty levels, faced a daunting task: to convince Americans - and an international audience - that the danger of Iraq's weaponry is so grave and so urgent that Hussein must be confronted now. Many U.S. allies insist that U.N. weapons inspectors in Iraq be given more time. Bush had to explain why there is no time to wait.

While foreign policy seemed to dominate the night, Bush also focused on the nation's struggling economy, a challenge that could all but consume a presidency in the absence of a foreign policy crisis. The president claimed credit for bringing the nation out of recession last year by proposing a tax cut shortly after taking office that, he said, put more money in the hands of consumers.

Bush argued that his proposed $670 billion tax-cut plan could bring new relief, helping small businesses and average families, and putting the nation on a path toward sustained growth within a few years.

"After recession, terrorist attacks, corporate scandals and stock market declines, our economy is recovering - yet it is not growing fast enough or strongly enough," Bush said. "Jobs are created when the economy grows. The economy grows when Americans have more money to spend and invest. And the best, fairest way to make sure Americans have that money is not to tax it away in the first place."

A year after the president stood in the same chamber enjoying sky-high approval ratings and the public's confidence that he could produce a vigorous recovery, the economy is still in the doldrums, and a majority of voters are beginning to hold Bush accountable.

Much of the early part of Bush's speech focused on the economy, as well as other domestic proposals, such as reforming Medicare, capping jury awards in medical malpractice lawsuits and promoting energy efficiency in the country.

Bush saved his most forceful rhetoric for the last part of his speech, when he spoke of Iraq before a House chamber full of lawmakers, Cabinet officials and Supreme Court justices, who remained mostly silent as Bush talked about a possible war.

The president's stance reflects the policy of pre-emption he established after Sept. 11. That policy frees America to strike first against regimes or groups that could threaten the United States or its allies. Bush's policy has alarmed foreign leaders and drawn criticism at home, and last night was a crucial test of whether Bush can justify his approach.

But Bush also spoke at a moment when Americans are alarmed about the struggling economy, fearful about jobs and doubtful that the prosperity and economic vigor of the 1990s will return anytime soon. Mindful that a sour economy alone can topple otherwise successful presidencies, Bush sought last night to convince Americans that he recognizes the nation's economic ills and has the right remedies.

His challenges are severe. Polls have shown that while most Americans favor ousting Hussein by force, they believe that Bush has failed to provide compelling evidence that Iraq possesses weapons of mass destruction and poses an immediate threat. A large majority says that the United States should not attack alone, without the support of the United Nations and other allies.

Polls also show that only about 45 percent of Americans approve of Bush's handling of the economy, just barely higher than his father's approval ratings on the economy at the same time in his first and only term. Surveys show that a majority of Americans believe that Bush's $670 billion tax cut, which he proposed this month, would mostly benefit the wealthy. Democrats have attacked the president's plan, saying it would do little to stimulate the economy and would increase federal budget deficits for years to come.

As he always has in high-profile speeches, Bush turned in a commanding performance, speaking confidently and projecting the image of an engaged leader. But it will be days, perhaps weeks, before it will be known whether he succeeded in satisfying public doubts about Iraq and the state of the economy.

In a response to skeptics who believe Bush is rushing needlessly toward war, administration officials have said they will soon begin declassifying more evidence of Hussein's weapons programs. But, mindful of his sizable audience last night and the need to justify a march toward war, Bush took the opportunity to hold out some new evidence.

The president also sketched out a robust domestic agenda for the new year that has already drawn attacks from Democrats and will become the launching point for intense debate in Congress.

White House aides have said that the Republican takeover of the Senate after the November elections gives the president's policies a far better chance of passage. But at the same time, Democrats have viewed Bush's falling approval ratings as a green light to begin challenging him more openly.

Bush spoke last night about a contentious proposal to offer seniors a prescription drug benefit that may give them the choice to enroll in government-subsidized private health care plans. Democrats have insisted that any such benefit should be entirely operated by the federal government through Medicare. The president will travel to Michigan today to promote his prescription drug plan, the first of what is expected to be a handful of trips around the country to pitch his agenda directly to Americans.

Bush described his agenda as "compassionate," noting specifically that his proposal to open more federal funding to churches and other religious groups that provide social services would extend help to some of the nation's neediest people.

Adding a new element to that plan, Bush said he would direct federal agencies to make drug-treatment money, in the form of vouchers, available to addicts even if they seek help at religious organizations. Such a proposal has been criticized in the past because some churches and religious groups do not always employ staff with medical licenses.

The president also touched on his call for limits on damages awarded by juries in medical malpractice cases. In West Virginia, Pennsylvania and other states, some doctors have been forced to move or to close practices, unable to afford the rising cost of medical liability insurance.

The president and many Republicans say those costs have soared because trial lawyers have brought frivolous lawsuits against doctors and because, in some cases, juries have offered financial awards that were excessive. Democrats contend that mismanagement in the insurance industry is more to blame for the higher costs.

Bush also called on members of Congress to hold the line on federal spending this year, at a time when the country may need to fund a war in Iraq and is still conducting a global war on terrorism and funneling resources to a vast new Cabinet agency to protect the homeland.

Delivering the Democratic response to Bush's speech last night was Gov. Gary Locke of Washington state. In choosing Locke instead of a member of Congress, the party broke with tradition. But it also sought to send a message to the nation that state leaders are deeply worried that Bush's agenda is failing to give states enough money to pay for services in distressed economic times.

Following tradition, the first lady, Laura Bush, assembled guests in her box who the White House hoped would personalize Bush's message and his agenda.

The guests included a handful of people who would be expected to benefit from Bush's tax cut, several doctors who have suffered from high insurance costs, the director of a religious group that treats cocaine addicts and a Marine corporal who helped rescue people from the wreckage at the Pentagon on Sept. 11, 2001.

One of the seats in Mrs. Bush's box was left empty, to represent "the empty place many Americans will have" after the terrorist attacks 16 months ago.