“I don’t think anybody thinks we can contravene the laws of supply and demand any more than we can contravene the laws of gravity,” said David S. Cohen, who, as treasury under secretary for terrorism and financial intelligence, oversees the administration of the sanctions. But, he said, “We have flexibility here, and I think we have a pretty good opportunity to dial this in just the right way that it does end up putting significant pressure on Iran.”

The American effort, as described by Mr. Cohen and others, is more subtle than simply cutting off Iran’s ability to export oil, a step that would immediately send the price of gasoline, heating fuel, and other petroleum products skyward. That would “mean that Iran would, in fact, have more money to fuel its nuclear ambitions, not less,” Wendy R. Sherman, the newly installed under secretary of state for political affairs, warned the Senate Foreign Relations Committee earlier this month.

Instead, the administration’s aim is to reduce Iran’s oil revenue by diminishing the volume of sales and forcing Iran to give its customers a discount on the price of crude.

Some economists question whether reducing Iran’s oil exports without moving the price of oil is feasible, even if the market is given signals about alternative supplies. Already, analysts at investment banks are warning of the possibility of rising gasoline prices in 2012, due to the new sanctions by the United States as well as complementary sanctions under consideration by the European Union.

Since President Obama’s first months in office, his aides have been talking to Saudi Arabia and other oil suppliers about increasing their production, and about guaranteeing sales to countries like China, which is among Iran’s biggest customers. But it is unclear that the Saudis can fill in the gap left by Iran, even with the help of Libyan oil that is coming back on the market. The United States is also looking to countries like Iraq and Angola to increase production.

Daniel Yergin, whose new book, “The Quest,” describes the oil politics of dealing with states like Iran, noted in an interview that “given the relative tightness of the market, it will require careful construction of the sanctions combined with vigorous efforts to bring alternative supplies into the market.” He said that it would “add a whole new dimension to the debate over the Keystone XL pipeline,” the oil pipeline from Canada to the United States that the administration has sought to delay.

“The only strategy that is going to work here is one where you get the cooperation of oil buyers,” said Michael Singh, managing director of the Washington Institute for Near East Policy. “You could imagine the Europeans, the Japanese, and the South Koreans cooperating, and then China would suck up all of the oil that was initially going to everyone else.”