Democratic congressional leaders yesterday ripped into President Bush on the eve of his State of the Union address, assailing his administration's credibility and contending that Bush has not yet made the case for war against Iraq.

In a joint appearance at the National Press Club, Senate Minority Leader Thomas A. Daschle (D-S.D.) and his House counterpart, Rep. Nancy Pelosi (D-Calif.), accused the administration of creating a "credibility gap" by promising things it has no intention of delivering.

"History is full of politicians whose rhetoric is out of step with reality, who promise something and then fail to deliver," Daschle said. "But the Bush administration offers a credibility gap with a new twist: This is a White House that promises one thing knowing full well it is delivering another."

The leaders' tough comments came one day before Bush's televised address to a joint session of Congress, and belittled the president's Iraq policy at a time when he is struggling to rally U.S. allies.

Their attack marked a low point in the deteriorating relations between the White House and congressional Democrats. Democratic strategists said the party, smarting from losses in November's elections, is determined to use Bush's address to spread doubts about his leadership, which have become evident in recent polls.

Marc Racicot, chairman of the Republican National Committee, vigorously defended Bush. Democratic leaders, he said, are "so blinded by political ambition and shallow opportunism that they are willing to hold press conferences to criticize in shrill and caustic tones the positions and proposals of the president that are not yet known to them."

The White House, heading into Bush's formal reelection campaign, is at pains to portray him as fully engaged on the economy and not just on Iraq. The first half of tonight's 50-minute speech will focus on health care and other domestic issues, followed by a discussion of national security and homeland security, including Iraq, aides said.

"Most of the State of the Union will not be about Iraq," press secretary Ari Fleischer said. "I think the American people have domestic concerns as a number one priority, and they're going to hear an awful, awful lot about that."

One section of the speech deals with what Bush's aides call his "compassion agenda." Sources said he will announce that the budget he releases Feb. 3 will include money to expand mentoring programs for prisoners' children and for middle-school students from lower-income families.

Sources said Bush also will announce plans to expand his faith-based initiative so that states can provide vouchers to people seeking drug and alcohol rehabilitation, allowing them to pay for treatment at centers run by religious organizations. Supporters of the change say it will allow the federal government to steer funding to religious organizations without directly funding them. Critics contend the plan will encourage treatment by people who are not certified or do not have master's degrees in social work.

Daschle and Pelosi offered several examples of what they described as Bush's false promises.

Daschle said the administration promises relief to middle-class families but "delivers a reward to wealthy investors. While promising to bring new accountability and responsibility to government, the White House runs up huge deficits -- and then blames it on the war."

The senator said Americans hear "mixed signals from the White House on everything from the economy to Iraq to North Korea. They sense the indecision on what to do about the war on terrorism. They see the shifts in direction, the false starts and the backsliding on basic promises."

Focusing mainly on Iraq, Daschle challenged Bush to explain why the threat is "so imminent that it justifies putting American lives at risk," and why the U.S. should short-circuit an inspections process it had demanded.

"If we have proof of nuclear and biological weapons, why don't we show that proof to the world -- as President Kennedy did 40 years ago when he sent Adlai Stevenson to the United Nations to show the world U.S. photographs of offensive missiles in Cuba?" Daschle asked.

"At a time when we have only just begun to fight the war on terror," he added, "the American people deserve to hear why we should put hundreds of thousands of American troops at risk, spend perhaps hundreds of billions of dollars, risk our alliances and inflame our adversaries to attack Iraq."

Pelosi said: "The administration says that the reason we cannot afford $1.5 billion in homeland security -- which the Congress passed into law but the president refuses to spend -- is that we are constrained by a wartime budget. And yet, the president says there is enough money in the wartime budget to create a huge tax cut that benefits the wealthiest in our country. The credibility gap widens."

White House aides said the largest new proposal in Bush's speech will be his call for Congress to make changes to Medicare that would help senior citizens pay for prescription drugs largely through private, managed-care plans. An administration official said the plan is expected to cost close to $400 billion over 10 years, although the details are not settled.

The White House's Web site, www.whitehouse.gov, plans to open a State of the Union section at 3 p.m. today. It is expected to include photos showing preparation of the address, as well as video interviews with Cabinet secretaries and other administration officials discussing the speech.

Bush is playing an unusually personal role before the speech. He talked with conservative columnists yesterday and planned lunch today with television anchors before heading to Capitol Hill.

At the National Press Club, House Minority Leader Nancy Pelosi (D-Calif.) accused the administration of a "credibility gap," saying it seeks a large tax cut while at the same time warning of the constraints of a wartime budget.Senate Minority Leader Thomas A. Daschle (D-S.D.) said Americans "deserve to hear why we should put hundreds of thousands of American troops at risk, spend perhaps hundreds of billions of dollars. . . ." President Bush practices his State of the Union speech. Half of the address tonight is to focus on domestic issues.