The Bush administration cautiously welcomed Iran's new willingness to negotiate over its disputed nuclear program on Tuesday, even as it intensifies efforts to use international trade and financial levers to pinch the clerical regime.

Iranian Foreign Minister Manouchehr Mottaki said Tuesday his country was ready for "negotiations on Iran's nuclear issue without any preconditions," a reference to suspended talks with European nations that would give Iran modest economic incentives to drop suspect nuclear activities.

"Trust but verify," White House press secretary Tony Snow replied, after saying the United States was glad that Iran would return to the table. "We'll just have to wait and see."

Snow said he hoped the talks would "produce productive results."

The administration previously has said Iran makes such pledges as a stalling tactic when international pressure mounts. At the State Department Tuesday, spokesman Sean McCormack noted that Iran has made similar promises in the past.

"Nothing new there," he said of the Iranian statement.

Iran left the European talks last year and recently resumed nuclear activities that it had voluntarily suspended during negotiations. Tehran has refused to give up its right to master all aspects of nuclear production, including uranium enrichment, which it says will be used only for peaceful nuclear energy.

The U.S. has accused Iran of hiding ambitions to build weapons, and has long tried to use the powerful United Nations Security Council, which can impose mandatory economic sanctions, to deter Iran.

The United States supported the European negotiations and waited until they faltered before making a push to take Iran's case to the Security Council this spring. Now that the case is there, the Bush administration has been unable to persuade Tehran's commercial partners Russia and China to take harsh steps.

As a backup, the U.S. is working increasingly publicly to line up banks and allies in Europe, the Persian Gulf and Asia to curb or cut off business with Iran. The Bush administration cites as a model the restrictions a Macao bank imposed last year on North Korea.

"This is something that we work on, for example, with other like-minded countries concerning North Korea, as well as other countries around the world," State's McCormack said Tuesday.

Officials from the State and Treasury departments have been traveling heavily in recent weeks, pushing for voluntary sanctions if the U.N. Security Council is unwilling to impose mandatory global restrictions and Iran refuses to back down.

The U.S. has little economic leverage over Iran by itself, since it cut almost all business and trade ties following the 1979 Islamic revolution and the storming of the U.S. Embassy in Tehran. Europe and Asia maintain strong economic ties with the oil exporter, and would thus by affected by the same voluntary financial strictures meant to hurt Iran.

President Bush called Russian President Vladimir Putin to discuss Iran on Tuesday, and Secretary of State Condoleezza Rice called her Russian counterpart ahead of meetings among the Security Council permanent membership later this week in Vienna, Austria.

European negotiators hope to present a new package meant to reward Iran if it gives up uranium enrichment activities — or penalize it if it doesn't — before Bush travels to Europe for a summit with the European Union on June 21.

At the State Department, McCormack said the ministers are close to agreement on the new package and hope to announce its contents this week.

The package would probably come with the threat of harsher Security Council action.

The Security Council gave Iran until the end of April to suspend disputed activities.

If Iran remains defiant, the resolution — as outlined to AP by diplomats familiar with a draft version of the text — calls for imposing sanctions under the U.N. Charter. But it avoids any reference to a specific article of the charter that can trigger possible military action to enforce any such resolution.

The proposal also calls for new consultations among the five permanent Security Council members on any further steps against Iran. That is meant to dispel complaints by the Russians and Chinese that once the screws on Iran are tightened, the council would automatically move toward military involvement.

Among the possible sanctions are a visa ban on government officials, freezing assets, blocking financial transactions by government figures and those involved in the country's nuclear program, an arms embargo and a blockade on the shipping of refined oil products to Iran.