Israel openly debating whether to strike at Iran’s nuclear facilities in the coming months, the Obama administration is moving ahead with a range of steps short of war that it hopes will forestall an Israeli attack, while forcing the Iranians to take more seriously negotiations that are all but stalemated.

Already planned are naval exercises and new antimissile systems in the Persian Gulf, and a more forceful clamping down on Iranian oil revenue. The administration is also considering new declarations by President Obama about what might bring about American military action, as well as covert activities that have been previously considered and rejected.

Later this month the United States and more than 25 other nations will hold the largest-ever minesweeping exercise in the Persian Gulf, in what military officials say is a demonstration of unity and a defensive step to prevent Iran from attempting to block oil exports through the Strait of Hormuz. In fact, the United States and Iran have each announced what amounted to dueling defensive exercises to be conducted this fall, each intended to dissuade the other from attack.

The administration is also racing to complete, in the next several months, a new radar system in Qatar that would combine with radars already in place in Israel and Turkey to form a broad arc of antimissile coverage, according to military officials. The message to Iran would be that even if it developed a nuclear weapon and mounted it atop its growing fleet of missiles, it could be countered by antimissile systems.

The question of how explicit Mr. Obama’s warnings to Iran should be is still a subject of internal debate, closely tied to election-year politics. Some of Mr. Obama’s advisers have argued that Israel needs a stronger public assurance that he is willing to take military action, well before Iran actually acquired a weapon. But other senior officials have argued that Israel is trying to corner Mr. Obama into a military commitment that he does not yet need to make.

On Sunday, Prime Minister Benjamin Netanyahu appeared to criticize Mr. Obama for being too vague about how far Iran can go. “The international community is not setting Iran a clear red line, and Iran does not see international determination to stop its nuclear project,” he told his cabinet. “Until Iran sees a clear red line and such determination, it will not stop the progress of its nuclear project — and Iran must not be allowed to have nuclear weapons.”

None of the steps being taken by the Obama administration addresses the most immediate goal of the United States and its allies: Slowing Iran’s nuclear development. So inside the American and Israeli intelligence agencies, there is continuing debate about possible successors to “Olympic Games,” the covert cyberoperation, begun in the Bush administration and accelerated under Mr. Obama, that infected Iran’s nuclear centrifuges and, for a while, sent them spinning out of control. An error in the computer code alerted Iran to the attack in 2010, and since then many of the country’s nuclear sites have been modified to defend against such attacks, according to experts familiar with the effort.

All of these options are designed to buy time — to offer Israeli officials a credible alternative to a military strike that would almost certainly trigger an Iranian reaction and, the White House and Pentagon fear, could unleash a new conflict in the Middle East. While Mr. Obama’s national security team has been very closed-mouthed about the tense discussions with Mr. Netanyahu, the chairman of the Joint Chiefs of Staff, Gen. Martin E. Dempsey, gave voice to the concerns in London on Thursday.

General Dempsey repeated the familiar American position that an Israeli attack would “clearly delay but probably not destroy Iran’s nuclear program.”

But then he went beyond any warning that Mr. Obama has given to Israel in public, saying that the international coalition of countries applying sanctions against Iran “could be undone” if the country was attacked “prematurely.” He added: “I don’t want to be accused of trying to influence, nor do I want to be complicit if they choose to do it.”

United States intelligence officials have said they have no evidence that Iran’s top leaders have decided to take the final steps toward a weapon. Iran’s intentions remain unclear, intelligence officials say.

Last week, the International Atomic Energy Agency reported an increase in the number of centrifuges that Iran has installed in an underground enrichment plant that is largely invulnerable to Israeli attack, but also indicated that Iran has converted some of its most highly enriched fuel to a form that would be difficult to use in a weapon.

The administration has already quietly proposed a “stop the clock” agreement to get Iran to halt production of the fuel that is closest to bomb-grade — and to ship it out of the country, according to diplomats from several countries involved in the discussions. But Iranian officials have rejected those calls, insisting on a lifting of all sanctions, and there has been no talk of a broader, more permanent deal.

Mitt Romney, Mr. Obama’s Republican challenger, has taken a harder line, saying he would never agree to allow Iran to enrich uranium at any level — a restriction even many Republicans, including some of Mr. Romney’s advisers, say there is virtually no chance Iran will accept, since it has a legal right to peaceful enrichment.

One option the administration has already approved is the military exercise, scheduled for Sept. 16-27, in which the United States and its allies will practice detecting and destroying mines with ships, helicopters and robotic underwater drones. The ships will stay out of the narrow Strait of Hormuz, to avoid direct interaction with Iran’s navy.

In advance of the exercise, the United States Navy earlier this summer doubled the number of minesweepers in the region, to eight vessels. The deployments are part of a larger series of military reinforcements into the Persian Gulf in recent months, all described by the United States as defensive.

That is also the explanation for the American efforts to create a regional missile defense system across the Gulf to protect cities, oil refineries, pipelines and military bases from an Iranian attack. The latest element is a high-resolution missile defense radar in Qatar, meant to stress that Iran’s Arab neighbors are as concerned about Tehran’s abilities as is Israel.

Military specialists said offensive military options, including strikes against Iran’s refineries and power grid, could also be telegraphed to the Iranians.

“The United States does not have to threaten preventive strikes,” Anthony H. Cordesman, a longtime military analyst at the Center for Strategic and International Studies, wrote in a recent paper, “Iran: Preventing War by Making It Credible.” “It simply has to make its capabilities clear in terms of a wide range of possible scenarios.”

But there is concern among American strategists that Iran could interpret these actions as encirclement, and that the actions could encourage those elements in the country that want to move faster to a nuclear “capability,” if not a weapon itself. Even one of the options that many Democrats and Republicans advocate to shake Iran — to help topple President Bashar al-Assad of Syria, Iran’s only real friend in the region — could have the same effect.

Inside the Obama White House, there has also been debate about whether Mr. Obama needs to reshape his negotiating strategy around clear “red lines” for Iran — steps beyond which the United States would not allow the country to go. Earlier this year Mr. Obama said he believed that the United States and its allies could not simply accept a nuclear Iran, largely because of the high risk that other Arab states would seek weapons.

Even if Mr. Obama set a clear “red line” now, its credibility may be questionable. According to a tally by Graham Allison, the Harvard expert on nuclear conflict, the United States and its allies have allowed Iran to cross seven previous “red lines” over 18 years with few consequences. That leaves one other option that officials are loath to discuss: new covert action.

The “Olympic Games” attack on Iran’s centrifuges was chosen over another approach that the Bush administration explored: going after electrical grids feeding the nuclear operations. But Mr. Obama has rejected any attacks that could risk affecting nearby towns or facilities and thus harm ordinary Iranians. Other plans considered in the past, and now reportedly back under consideration, focus on other targets in the nuclear process, from making raw fuel to facilities involved in missile work. One missile plant blew up last year, and Israeli sabotage was suspected, but never proven. American officials say the United States was not involved.

One other proposal circulating in Washington, advocated by some former senior national security officials, is a “clandestine” military strike, akin to the one Israel launched against Syria’s nuclear reactor in 2007. It took weeks for it to become clear that site had been hit by Israeli jets, and perhaps because the strike was never officially acknowledged by Israel, and because its success was so embarrassing to Syria, there was no retaliation.

But Iran’s is a much higher-profile program. “At best this would buy you a few years,” one administration official said, without acknowledging such a strike was under consideration by the United States or Israel. Even if an explosion at an Iranian facility was accidental, the official said, “the Iranians might well see it as a provocation for an attack of their own.”