U.S. Secretary of State Condoleezza Rice raised fresh doubts about the nature of Iran's nuclear program, saying if the country really wanted only an avenue to peaceful atomic energy it could quickly have it.

Instead, Iran is stonewalling on an attractive deal to trade away only the part of the program that could result in a nuclear weapon, Rice said ahead of a gathering of the U.N. nations that have presented a carrot-or-stick package to Iran.

"I continue to suspect this is not at all about a civil nuclear program," Rice told reporters traveling with her. Iran's insistence that it be able to enrich uranium on its terms seems at cross-purposes with that goal, Rice said Thursday.

"One has to wonder what is going on here."

U.S. intelligence agencies concluded in a report last year that Iran shelved an active weapons-development program years ago, a finding that undercut the Bush administration's claim that Iran was using a public energy development program to hide a secret drive for a bomb. An unclassified summary of the report, known as a National Intelligence Estimate, said Iran could resume a weapons program and might evade detection if it did. Rice did not say whether she thought that had happened and did not directly accuse Iran of lying.

Iran insists its program is peaceful but says it is an affront to give up full ownership of nuclear processes that Western nations possess. Israel is also assumed to possess nuclear weapons and the technology that would be at least temporarily withheld from Iran under the proposed international bargain.

Analysts have suggested that Iran may be deliberately leaving ambiguities about its program as a negotiating tactic and to project strength as it competes with the United States for influence in the Middle East. Other analysts say it is probably inevitable that Iran will acquire the bomb.

Rice is meeting Friday with other permanent, veto-wielding members of the U.N. Security Council to discuss the next step with Iran. The session in London could be contentious, and Rice tried to play down expectations for a clear agreement on what to do next.

The U.S. was a main driver in the passage of three rounds of mild U.N. sanctions, the sticks that the U.S. thinks are more likely to get Iran to back down. But the U.S. has also bowed to other partners who want to try to entice Iran by offering more or better carrots. There is a potential fight brewing over what those incentives might be.

"There is a desire, I think, on the part of some participants to look again at the package we have and say, 'Is this everything we want to do in the package?"' Rice said. "I don't mind continuing to look at the package, but this is a generous package" already, she said.

The U.S. contention that Iran covertly sought a weapon was an important ingredient in winning any sanctions, and the Bush administration has scrambled since the National Intelligence Estimate findings were made public to say that Iran remains a threat. The Security Council approved the latest round of sanctions after the NIE was released.

In Washington, the chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, added more U.S. pressure on Iran, telling the American Jewish Committee on Thursday night that Iran's "pursuit of nuclear weapons and their pursuit of terrorism is the perfect nightmare that is a threat to Israel and the rest of the region."

On another issue concerning Iran, Rice said the U.S.-backed government in Iraq informed the Bush administration ahead of time about a planned face-to-face meeting with the Iranians over alleged Iranian support for militants and insurgents in Iraq.

"He is engaging his neighbor about what it would be useful to have Iran do," Rice said, referring to Iraqi Prime Minister Nouri al-Maliki.