Senate Democratic Leader Tom Daschle challenged the Bush administration on Monday to show "proof to the world" that Iraq has weapons of mass destruction, part of an attack by the party's top leaders on the eve of the president's State of the Union address.

In a joint appearance, Daschle and House Democratic Leader Nancy Pelosi accused Bush of creating a "credibility gap" on purpose, of saying one thing and doing another across a range of issues.

"The administration says that the reason we cannot afford $1.5 billion in homeland security funding, which the Congress passed into law but the president refuses to spend, is that we are constrained by a wartime budget," Pelosi, D-Calif., said in prepared remarks.

"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," she added.

Pelosi's criticism of Bush was directed largely at domestic issues, including the president's proposed elimination of the tax on corporate dividend and his record on the environment.

Daschle focused largely on foreign policy, challenging Bush to explain his emphasis on Iraq.

"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 said in prepared remarks.

"At a time when we have only just begun to fight the war on terror, 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."

Daschle's reference to Cuba related to the Cuban missile crisis of four decades ago. At the time, the Kennedy administration unveiled reconnaissance photographs at the United Nations to prove its claim that the Soviet Union had dispatched missiles to an island 90 miles off the United States mainland.