As the Bush administration pushes to refer Iran to the U.N. Security Council, many members of Congress support keeping the use of military force as an option to thwart Tehran's nuclear ambitions.

Lawmakers largely back the effort to haul Iran before the Security Council over the Iranian government's refusal to give up its uranium enrichment program. But some say they doubt that a simple reprimand from the council -- seen as a likely outcome -- will be enough to persuade Iran to change course.

Rather, Republicans and Democrats alike say the United States should seek international economic sanctions that are harsh enough to hurt Iran, while securing assurances from Tehran's major trading partners that they will abide by any restrictions the Security Council imposes.

Secretary of State Condoleezza Rice has repeatedly emphasized that the United States is committed to addressing the Iran standoff diplomatically and is working to line up support for a vote of the U.N.'s International Atomic Energy Agency to refer Iran to the Security Council.

A British Foreign Office official said Wednesday that foreign ministers from the five permanent Security Council members -- Britain, France, Russia, China and the United States -- plus Germany will discuss the situation with Iran while in London next week for a donors' conference on Afghanistan.

In Moscow, Iran's top nuclear negotiator said Wednesday that Tehran views Russia's offer to have Iran's uranium enriched in Russia as a positive development but no agreement has been reached between the countries.

Chief negotiator Ali Larijani also reiterated Iran's threat to renew enrichment activities if it is referred to the U.N. Security Council.

Rice has shied away from discussions of possible U.S. military action, saying the United States is focused on a diplomatic course. But she has consistently said President Bush reserves the right to use any option, including force.

Lawmakers say the threat that Iran could obtain weapons of mass destruction is so serious that the international community must act decisively to halt Iran's nuclear program. The Bush administration should not rule out other avenues should diplomatic efforts fail, they say.

"It's important to give diplomacy a try, but I don't believe we should take any option -- including military force -- off the table," said Sen. John Cornyn, R-Texas, chairman of the Senate Armed Services emerging threats subcommittee.

"If you eliminate the threat of military action, the possibility of it, then there's no way to secure compliance," added Rep. Gary Ackerman, D-N.Y., a House International Relations Committee member.

The standoff with Iran over its nuclear program has intensified in the month that Congress has been away from Washington for its holiday break.

Iran has broken U.N. seals at a uranium enrichment plant and said it was resuming nuclear research after a 2 1/2-year hiatus. European countries declared dead their negotiations with Iran over its nuclear program.

The Iranian government claims its intention is purely peaceful -- to generate electricity. But the United States and its allies fear Iran has a more threatening objective -- making nuclear bombs.

Sen. John McCain, R-Ariz., said diplomatic efforts must be exhausted before turning to the "last option," the use of force.

"There's only one thing worse than the United States exercising a military option, and that is Iran having nuclear weapons," the No. 2 Republican on the Senate Armed Services Committee said on "FOX News Sunday."

Some analysts have said that while an American military strike could destroy Iran's nuclear facilities, it would anger U.S. allies, intensify the Muslim world's bitterness toward the United States, drive up oil prices and rally Iranians behind their president, Mahmoud Ahmadinejad.

Sen. Barack Obama, D-Ill., said all options, including military force, should be on the table. But, he said that for now, the United States and European countries must do everything possible to secure the support of China and Russia to take Iran before the Security Council, and then stake out "a tough posture" that includes sanctions.

However, said Obama, a Senate Foreign Relations Committee member, "We have to be judicious in how we apply sanctions -- there may be some sanctions that may not make a difference."

Rep. Christopher Smith, R-N.J., vice chairman of the House International Relations Committee, said: "We need to use the diplomatic means very, very aggressively."

Some lawmakers are suggesting that new Iranian leadership is needed.

Sen. Jon Kyl, R-Ariz., said that for now, the United States and its allies must intensify its pressure on Iran to halt its nuclear program. "But ultimately," he said, "there must be change in the country's leadership. The current Iranian government is a corrupt and dangerous regime that's out of step with its citizens."

Cornyn said Iran has become more authoritarian and autocratic. "We need to do a better job of letting pro-democracy forces in Iran know that we are supportive of their efforts of peaceful regime change," he said.

Over the past week, several senators have proposed resolutions that ranged from condemning Tehran for its nuclear activities to accusing Bush of ignoring the threat of Iran.

But given the widespread interest in putting the Senate on record with its concerns about Iran, congressional officials say several Republicans and Democrats are working together to write one resolution that they hope will gain broad bipartisan support and can be introduced by next week.