WASHINGTON — Legislation codifying American support for democratic forces in Iran to choose their form of government is moving quickly through the Senate after passing the House yesterday by a voice vote.

The bill, known as the Iran Freedom and Support Act, marks a small victory for the forces within the Bush administration and the Senate that have favored more robust support for Iran’s liberal opposition. At the same time, it is also a compromise. The legislation, sponsored by Senator Santorum, a Republican of Pennsylvania, no longer calls for free elections in Iran.

Instead, the bill says it “should be the policy of the United States to support efforts by the people of Iran to exercise self-determination over the form of government of their country.” To that end, the legislation also says America should “support peaceful pro-democracy forces in Iran.”

The measure specifically does not authorize military action, but in the same way the Iraq Liberation Act of 1998 foreshadowed events in the Gulf, the latest bill may come to be seen as an upping of the ante with the Islamic regime — or a step or two short of war. Backers of the bill stress that they do not want it to be seen as a war measure; Mr. Santorum has said he does not favor an American invasion of Iran but supports the nonviolent struggle of Iranian liberals to effect a velvet revolution similar to the collapse of communism in Eastern Europe and the triumph of democracy in Ukraine.

Language in the bill is certainly a far cry from calling for regime change, but it could resemble the “meddling” that President Talabani of Iraq promised would be the consequence should countries like Iran and Syria continue to back terrorists seeking to sabotage the elected government in Baghdad.

The entire bill, which also reauthorizes rarely enforced sanctions against foreign companies that invest in Iran, is the product of intense negotiations over the last four days among the White House, State Department, House, and Senate. Initially, the White House opposed Mr. Santorum’s bill, as it did when the senator tried to attach it to a June resolution supporting the State Department’s new policy to offer to negotiate directly with Iran if it suspended its enrichment of uranium.

When Mr. Santorum introduced his bill on the Senate floor on June 15, Senator Biden of Delaware, the ranking Democrat on the Senate Foreign Relations Committee, said he had just spoken with Secretary of State Rice, who urged him not to support the proposal.

But the White House, which is accepting applications from Iranian democrats for a new $70 million aid program and has beefed up radio broadcasts into Iran, also has said Iranian democracy — if not regime change — is a goal of its foreign policy. Indeed, President Bush this month addressed the Iranian people directly in his speech at the U.N. General Assembly, saying he supports their struggle for a better government.

Earlier versions of Mr. Santorum’s bill asked for $100 million in prodemocracy assistance, but the legislation has no dollar figure now.

The timing of the bill’s passage in the House coincides with both a legislative and diplomatic calendar. With the 109th Congress set to recess by Saturday at the latest, the Senate is expected to vote and pass the bill Friday or Saturday, though late yesterday evening some Democratic senators raised procedural concerns about calling for a vote on Mr. Santorum’s bill. Nevertheless, its expected passage in the Senate will coincide with last-minute European-led negotiations with Iran to entice the country to live up to its earlier agreements to suspend the enrichment of uranium.

The Iran bill fires a warning shot to Russia and China, two permanent members of the U.N. Security Council that could veto any U.N. sanctions against Iran in the future. The legislation says America must not “bring into force an agreement for cooperation” with any country selling advanced conventional weapons or missiles, or assisting Iran’s nuclear program. Both China and Russia have conducted a lucrative arms trade with Iran. The International Atomic Energy Agency has found both Russian- and Chinese-made equipment at Iran’s nuclear facilities, though the agency has yet to say whether the places it has inspected are used for military purposes.

The House’s passage of the bill is a particular victory for Mr. Santorum, who is in a tough race for re-election to the Senate in Pennsylvania. On September 18, Senator Lautenberg, a Democrat of New Jersey, and Rep. Allyson Schwartz, a Democrat of Pennsylvania, held an event in Pennsylvania challenging the Mr. Santorum’s rhetoric on Iran. According to a press release from the National Jewish Democratic Council, the two lawmakers accused Mr. Santorum of opposing specific legislation to punish Halliburton, the oil services giant formerly headed by Vice President Cheney, for allowing its subsidiaries to do business in Iran.

Halliburton was able to enter a partnership with Iranian energy concerns in part because of waivers built into the original executive order authorizing sanctions on Iran passed under President Clinton. Mr. Santorum’s legislation would close the loophole for future transactions between Iranian companies and American foreign subsidiaries.