OAKLAND, Calif.  Senator Clinton is moving to tie President Bush's hands with respect to Iran by endorsing legislation that would prohibit military action against the regime in Tehran without prior approval from Congress. "I believe the president has squandered our trust and that's why we need this legislation. If the president believes that the use of force against Iran is necessary, he must come to the Congress and make the case to the American people," Mrs. Clinton said during a speech here yesterday. "It would be a mistake of historic proportions if the administration thought anything Congress ever passed would give it the right to use force against Iran without further, explicit congressional authorization."

Mrs. Clinton noted that she issued a similar warning to Mr. Bush in a Senate floor speech earlier this year. However, she is now coupling that salvo with support for a bill Senator Webb of Virginia, a Democrat, is planning to introduce that would deny spending authority for any military operation against Iran.

The former first lady was quick to insist that the measure would not hamper the ability of American soldiers in Iraq to respond to attacks from Iranian forces or their allies. "This legislation would not infringe on the ability of our troops to protect themselves against attack from Iran or by Iranian surrogates. We never take away the right of self-defense," she said.

By endorsing the Iran legislation, Mrs. Clinton is continuing to tack through the rocky shoals of Democratic Party opinion on war-related issues. At a debate last week, a former senator from North Carolina, John Edwards, and a former senator from Alaska, Mike Gravel, both chastised Mrs. Clinton for voting for a nonbinding measure to designate Iran's Revolutionary Guard as a terrorist organization.

Mr. Edwards said passing the resolution could prompt Mr. Bush to claim he had congressional permission for an attack on Iran. "You cannot give this president the authority and you can't even give him the first step in that authority because he cannot be trusted," Mr. Edwards said.

Mrs. Clinton defended her vote on the Iranian Revolutionary Guard resolution yesterday, saying she backed the measure "in order to gain leverage in our diplomatic efforts."

The new legislation proposed by Mr. Webb and Mrs. Clinton could prove to be little more than symbolic. It may not get enough support to clear the Senate, could face a veto by Mr. Bush, and might well violate the Constitution by constraining the president's authority as commander in chief. Still, Mrs. Clinton's endorsement of the measure underscores how concerned she is about being painted as a closet militarist by liberal Democratic activists.

A supporter of pro-Israel causes who is backing Mrs. Clinton's presidential bid, Steve Rabinowitz, said her support for the funding restriction did not signal that the former first lady has turned soft on Iran.

"She has been as tough on Iran as anyone could reasonably expect," Mr. Rabinowitz, a former aide to President Clinton, said. "Let's keep in mind that requiring congressional authority doesn't mean you don't have a willingness to give it."

In a separate development, Mrs. Clinton made further inroads into Senator Obama's potential base yesterday by winning the endorsement of a longtime African-American congressman who now serves as mayor of Oakland, Ronald Dellums. "This is a pivotal moment. This is not about symbolism. This is about substance," Mr. Dellums said in an apparent reference to expectations that he would endorse or at least avoid snubbing the presidential bid of Mr. Obama, who is partly of African descent.

"I believe that history will record you will go down as one of the greatest presidents that ever led this country further into the 21st century," Mr. Dellums declared as he stood next to Mrs. Clinton at a community college in Oakland.

Mr. Dellums praised Mrs. Clinton's urban policy agenda, which he said contained "a magnificent statement of the plight of thousands and thousands of our young people that we are grinding up like glass in this country."

Earlier, Mrs. Clinton attended two fund-raisers, including one at a Tiburon, Calif., home with a sweeping view of the San Francisco Bay. Between 300 and 400 people paid $500 or more to attend the "sold out" breakfast. "I thought her speech was magnificent," one attendee, Jennifer Traeger-Hirschfelder, 37, of San Francisco, said.

Ms. Traeger-Hirschfelder said she was supporting Mrs. Clinton in part because her seasoning would serve her well. "She had been through the ringer when her husband was president. Now she really knows how to sling it right back," Ms. Traeger-Hirschfelder said. "I like John Edwards and Barack Obama, but I'm really not sure they would know what you have to do to deal with that."