WASHINGTON — The Obama administration is increasingly concerned about how long Iran may take to respond to its peace overture, and worried that delays will build pressure at home and abroad that could undermine the effort to overcome decades of antagonism through face-to-face talks.
In March, President Obama videotaped an appeal addressing Iranian leaders. But U.S. officials now worry that Tehran, currently engaged in a presidential election campaign, may not provide an answer until autumn or even the end of the year.
"We haven't gotten a clear message," said one U.S. official, who spoke on condition of anonymity because of the sensitivity of the subject. "It's not clear when it's coming."
Meanwhile, pressure is growing from U.S. lawmakers and Israeli officials not to allow Iran to delay its answer indefinitely. They argue that Tehran could use the time to continue working on what many nations believe is a nuclear weapons development program but Iran says is aimed at civilian energy production.
Hoping to improve the chances of success for Obama's overture, the administration has sharply narrowed the focus of possible discussions. Officials have decided that they won't seek at first to negotiate a wide range of issues with Iran, such as Tehran's support for the Hamas and Hezbollah militant groups, but will focus on the chief concern of the U.S. and its allies: Iran's nuclear research program.
Engagement with Iran has been one of Obama's top foreign policy initiatives, and senior officials meet daily to discuss how to move forward. Dennis Ross, a veteran U.S. diplomat and Middle East expert who is overseeing a review of Iran policy, has been in the region this week to consult with Arab leaders.
Israeli officials have suggested that Obama set a deadline for the overture. The administration has been noncommittal about a deadline, but officials have said they are aware that time is a key concern.
U.S. officials say the Iranians have made it clear that they won't talk until sometime after their June 12 presidential election, and perhaps not until the next president takes office in August.
Tehran could make its decision known at the September meeting of the United Nations General Assembly, but it is also possible that the process will take longer, officials said.
U.S. officials are still developing their own offer, but also are consulting allies to work up a common set of new political and economic sanctions that could be imposed if talks faltered.
U.S. lawmakers have been sending signals that their patience is not limitless. Bipartisan groups in both legislative chambers last month introduced measures to impose crippling sanctions on businesses profiting from deliveries of gasoline to Iran, which imports 40% of its supply.
Lawmakers said the goal was to bolster diplomatic efforts, but it was also a reminder to the administration. "If we are serious about stopping the emergence of a nuclear Iran, our window for effective diplomacy is starting to close," Rep. Mark Kirk (R-Ill.) said last week.
Some analysts said the legislation could harm U.S. diplomatic efforts. Europe is working closely with the United States on Iran, but may object to such a harsh step. The tough sanctions also could enable Iran's hard-liners to argue that the United States is not serious about the diplomatic opening.
Robert Wood, chief spokesman for the State Department, said officials were "reviewing" the proposed legislation. "It's important that it doesn't interfere with our ability to conduct diplomacy," he said.
Karim Sadjadpour, an Iran specialist at the Carnegie Endowment for International Peace, said the administration was caught in a conflict between two competing clocks: one timing the steady progress of Iran's nuclear program, and a second following the slower process of repairing the damage to U.S.-Iranian relations that has occurred over the last 30 years. "The second one is going to take a lot more time than the first," he said. "That's going to be difficult for the Obama team to reconcile."
Some Iran specialists within and outside government have long argued that the U.S. should try to open broad negotiations with Iran on all top issues, including Tehran's support for Islamic militants, and what the United States considers its dangerous meddling in Iraq and Lebanon. The idea of wrestling with all the issues at once is sometimes called a "grand bargain" approach.
But the administration has decided that it would be "just too big a bite of the apple," said one official familiar with the discussions.
The subject is no longer under discussion in the internal deliberations, he said.
Officials said they intend to press such issues later. They are also trying separately to win Iranian cooperation in areas where they believe the two countries have common goals.
In March, at an international meeting on Afghanistan, Richard C. Holbrooke, the special representative to Afghanistan and Pakistan, met briefly with Iran's deputy foreign minister and proposed further contacts on the subject.