WASHINGTON — Tensions are mounting among America, Switzerland, and Austria over commercial dealings that the central European states have with Iran. This week, the Swiss foreign minister announced a new natural gas deal with Iran and said she hoped it would pave the way for more robust bilateral relations between the two nations.

The announcement prompted the State Department to launch a legal review of American sanctions to examine whether Swiss firms should be denied access to financial markets here.

The announcement of the Swiss deal, under which liquefied natural gas is to be delivered starting in 2011, came as a prelude to a similar deal between Iran and an Austrian semi-national oil company, OMV, in which the state of Austria owns a little more than a 31% stake. A portion of that deal — which could be worth as much as $28.8 billion — for development of the Danan region is expected to be inked this month. The Swiss deal with Iran is worth a little more than $1 billion a year over a period of 25 years.

Talking to reporters this week in Bern following her unannounced visit to Iran, the Swiss Foreign Minister, Micheline Calmy-Rey, said her government did not need to ask America permission to pursue its national interests. “Switzerland is an independent country that has its own strategic interests to defend,” she said.

A spokesman for the State Department, Tom Casey, said, “Certainly, in terms of U.S. domestic law and policy, there are implications or potential implications for any kind of arrangement of this sort in terms of the Iran Sanctions Act.” He added, “And, obviously, as we get more details about this, we’ll be looking at that particular deal in the light of U.S. law and see whether it crosses any lines there.”

In Israel, the foreign ministry summoned the Swiss ambassador in Tel Aviv and criticized the decision to pursue the deal as “an unfriendly act.”

The timing of the Swiss deal, coming on the heels of a third resolution recently passed by the U.N. Security Council and an American-led effort to ban Iranian banks from the international financial system, jeopardizes the Bush administration’s grand strategy against Iran. Since Iran announced in 2006 that it had begun spinning centrifuges in its Natanz facility, President Bush has offered the carrot of direct engagement with Iran as a reward if Tehran ends the enrichment of nuclear fuel and the stick of diplomatic and financial sanctions if the mullahs did not comply. They have not complied, and the Treasury Department has steadily increased pressure on Iranian banks.

On Thursday, the Treasury Department issued a special circular warning American banks away from any interactions with nearly all of Iran’s banks. The Paris-based Financial Action Task Force consortium of banks and treasuries issued a warning at the end of February on Iran’s banks with regard to support for terrorism and money laundering.

The deputy director for research at the Washington Institute for Near East Policy, Patrick Clawson, said he doubts the Swiss will ever receive the liquefied natural gas, as there is currently no pipeline that connects Iran to Europe. “I am unaware of what means Iran has to transport natural gas to Switzerland. Iran at various times has announced plans for exporting liquefied natural gas from Iran, but Iran has never secured the financing. Nor is it apparent Iran will have the capacity for enough production of natural gas, because of the exploding demand for natural gas at home. They almost had to shut off natural gas to Tehran this winter,” he said.

Mr. Clawson noted that the visit of Foreign Minister Calmy-Rey was in keeping with a Swiss foreign policy that has sought to engage Iran more than other European countries have.

“Switzerland has had an active diplomacy in trying to encourage Iran to settle the nuclear dispute, and Switzerland has thought there had to be inducements to resolve the nuclear issue. Economic engagement is one of those inducements that have been much talked about as a way to persuade Iran to cooperate with the West,” he said. It was Switzerland’s ambassador to Iran, Tim Guldimann, who on May 2, 2003, faxed an alleged peace offer from Iran to the State Department. Senior Bush administration diplomats at the time, such as Richard Armitage, have since cast doubt on the offer and suggested that Mr. Guldimann’s fax was not a genuine olive branch.

For now, the Bush administration is watching closely the movements of the Austrians. The spokeswoman for an Austrian civic group that tracks Austrian ties with Iran, Stop the Bomb, Simone Hartmann, said that she is expecting the OMV deal to go through as soon as this month. “This is certainly important. Sanctions are the only way we can prevent Iran from becoming nuclear without force. We have to try every option to prevent Iran from becoming nuclear. It is crucial to use every option we have in this regard,” she said.