Secretary of State Condoleezza Rice said Tuesday there's no point in talking to Iran unless the clerical regime changes its behavior and gives up its suspected nuclear weapons ambitions.

Rice said true diplomacy "is not a synonym for talking," but must be combined with pressure tactics.

Speaking to the pro-Israel group AIPAC, Rice made it clear she doesn't believe Iran has quit pursuing a nuclear bomb.

There may be a time to engage the Iranians, but "not while they continue to inch closer to a nuclear weapon under the cover of talk," Rice said.

The secretary posed a series of rhetorical questions to cast doubt on Iran's claim that its nuclear program is purely peaceful and for civilian purposes. She asked why Iran has allegedly not been forthcoming with the U.N. nuclear agency and why part of its program is run by the military. She also pointed to a new skeptical report by U.N. nuclear watchdog Mohamed ElBaradei.

"It's just hard to imagine that there are innocent answers to these questions," Rice said.

Israeli Prime Minister Ehud Olmert was scheduled to address the lobby group later Tuesday.

Olmert, embattled politically at home, could be making his last trip to Washington as Israel's leader. He planned to discuss Israeli-Palestinian peace efforts and Iran with Rice and President Bush on Wednesday.

Israeli newspapers have reported that Olmert also hopes to acquire a sophisticated U.S. missile defense system, advanced radar and new warplanes.

But the visit is being overshadowed by Olmert's legal troubles at home, where a corruption investigation has decimated his popularity ratings and fueled growing calls for his dismissal.

The normally talkative Israeli leader did not emerge from his private quarters to speak to reporters during an overnight flight from Israel, arriving in Washington a couple of hours before dawn Tuesday.

White House press secretary Dana Perino said Tuesday that Bush is thinking about the Mideast peace negotiations, not Olmert's political problems. "Our focus hasn't been on that," she said. "President Bush has to keep his focus on the big picture. He's not spending a lot of time worried about that."

Rice told AIPAC that the U.S.-backed peace talks offer the best chance for a meaningful settlement of the six-decade conflict in the Middle East, but she also said the diplomatic process must carry over to the next U.S. president.

Olmert's trip comes at the height of the worst crisis of his two-year term. Israeli prosecutors are looking into hundreds of thousands of dollars in contributions that Olmert received from American donors in the years before he became prime minister.

Last week, the key witness in the case, American Jewish businessman Morris Talansky, said he gave Olmert cash-stuffed envelopes over 15 years, in part to help fund a penchant for luxury goods and five-star hotels. The testimony devastated Olmert's already compromised credibility and sent his popularity plummeting.

Olmert, who has weathered four previous police investigations since he took office, has said he will step down if indicted. But that has not helped ward off his political opponents.

Last week his key coalition partner, Defense Minister Ehud Barak, issued him an ultimatum: Step aside or Barak's Labor Party will topple the government and bring about new elections, more than a year ahead of the scheduled March 2010 vote.

On Monday, Barak told Labor lawmakers that he has drawn up the necessary legislation to dissolve the parliament — a move that would likely win approval in the 120-seat house. Barak did not say when he would submit the bill for a vote, but said elections this year are "entirely possible."

Olmert, meanwhile, has tried to project a business-as-usual appearance, meeting Monday with Palestinian President Mahmoud Abbas to discuss the status of peace talks before heading to Washington.

With Bush looking on, Olmert and Abbas relaunched peace talks last November after seven years of Israeli-Palestinian fighting. The two leaders have set a year-end target to reach a blueprint for peace before Bush leaves office.

But those talks appear to have made little progress. Olmert's woes and the increasing likelihood that Israel is heading for new elections make it unlikely that goal will be reached or that Bush and Olmert will still be around to see the results of the process they launched in Annapolis, Maryland.