Mr. Dalton said Iran imports 40 percent of its gasoline. Other analysts say the figure has dropped to 25 percent as Iran has constructed new refineries.
Mr. Dalton said there is general agreement that additional sanctions could effectively be imposed in the areas of arms sales, transport links, finance and insurance as well as investment in Iran’s oil and gas industry.
Mr. Jacobson said more could be done to enforce sanctions already approved against Iranian banks and arms transfers. He suggested that the United Nations could create a team to monitor sanctions as it has done regarding al Qaeda, Sudan and North Korea.
Given heightened concern over Iranian intentions, the French government has said that the 27-member European Union likely could be persuaded to take unified punitive measures if the U.N. Security Council fails to do so.
“Before some countries could get away with saying that it’s not urgent,” said the Foreign Ministry official in Paris.
Under the George W. Bush administration, Europeans blamed U.S. policies that set preconditions on negotiations with Iran.
Now, the official said, “We would expect agreement across the EU. … There’s a new American administration, and if it imposes strong sanctions, it would be difficult for it not to do the same.”
Barbara Slavin in Washington and Nicholas Kralev in Berlin contributed to this report.