ASHKELON, Israel -- A series of public statements and private communications from the Israeli leadership in recent weeks set off renewed concerns in the Obama administration that Israel might be preparing a unilateral military strike on Iran, perhaps as early as this fall.
But after a flurry of high-level visits to Israel, including one Wednesday by Defense Secretary Leon Panetta, a number of administration officials say they remain hopeful that Israel has no imminent plans to attack and may be willing to let the United States take the lead in any future military strike, which they say would not occur until next year at the earliest.
The conversations are part of delicate U.S.- Israeli negotiations that have intensified over the past month. On Wednesday, they continued with Mr. Panetta, who appeared with Israeli Defense Minister Ehud Barak and declared that the United States would stand by Israel if Iran developed a nuclear weapon. "We have options that we are prepared to implement to ensure that that does not happen," Mr. Panetta said.
Standing with Mr. Barak in front of an Israeli anti-rocket missile battery in the southern town of Ashkelon, about five miles from the Gaza border, Mr. Panetta made clear what he meant: "My responsibility is to provide the president with a full range of options, including military options, should diplomacy fail," he said.
In the last three weeks, a steady stream of administration officials has flown to Israel to meet with Prime Minister Benjamin Netanyahu -- among them, Secretary of State Hillary Rodham Clinton and national security adviser Thomas Donilon. The trips were planned in part for other reasons; Ms. Clinton and Mr. Panetta were going to Egypt to meet with its new president and so, diplomatically, couldn't ignore Israel. But administration officials say there has been an intense effort to stay in close contact with Israel and keep abreast of its intentions.
The visits, deliberately or not, also sandwiched in Mitt Romney, the presumptive Republican presidential nominee, who was in Jerusalem two days before Mr. Panetta. Mr. Romney, who received a short briefing from the U.S. ambassador in Israel but had no other substantive communication with the administration, appeared to take a harder line against Iran than President Barack Obama has.
In Jerusalem, Mr. Netanyahu continued Wednesday with his tough rhetoric of recent days, arguing that sanctions against Iran were largely useless. "Right now, the Iranian regime believes that the international community does not have the will to stop its nuclear program," Mr. Netanyahu said. "This must change, and it must change quickly, because time to resolve this issue peacefully is running out."
Administration officials say Israeli officials are less confrontational in private, and that Mr. Netanyahu understands the consequences of military action for Israel, the United States and the region. They say they know he has to maintain the credibility of his threat to keep up pressure on the United States to continue with sanctions and development of military plans.
"The more the Israelis threaten, the more we respond by showing them that we will take care of the problem if it comes to that," said Martin Indyk, a former U.S. ambassador to Israel and director of foreign policy at the Brookings Institution.
Mr. Panetta met separately Wednesday with Mr. Netanyahu, Mr. Barak and Israeli President Shimon Peres. Administration officials said the U.S. and Israeli officials shared the latest Iran intelligence, coordinated implementation of the most recent sanctions and discussed military options. Mr. Panetta said Tuesday in Cairo that he was not bringing any U.S. attack plans to show to the Israelis. He also said any U.S. strike would be a last resort.
"We have to exhaust every option, every effort, before we resort to military action," he said at the Askelon missile battery, which is part of the Iron Dome defense system in part paid for by the United States.
On Wednesday, Mr. Panetta used some of his sharpest language on Iran, as if to assure the Israelis that the Obama administration could be equally tough. "This is not about containment," he said to reporters at the start of his meeting with Mr. Peres. "This is about making very clear that they are never going to be able to get an atomic weapon."
In Israel, there remains feverish speculation that Mr. Netanyahu will act in September or early October. Besides the prime minister's fear that Israel's window of opportunity will close soon, analysts cite several reasons for the potential timing:
Israel does not like to fight wars in winter. Mr. Netanyahu feels that he will have less leverage if Mr. Obama is re-elected, and that if Mr. Romney were to win, the new president would be unlikely to want to take on a big military action early in his term. "If I were an Iranian, I would be very fearful of the next 12 weeks," said Efraim Halevy, a former chief of Israel's intelligence agency and national security adviser.
U.S. defense officials and experts in Israel say that because Israel does not have a bomb powerful enough to penetrate Iran's underground uranium-enrichment facilities, an independent strike would likely set the nuclear program back only one or two years, at most. That has led to major dissent among Israel's security professionals over the wisdom of such an attack.
The Pentagon, in contrast, has munitions, bombers, missiles, and stealth aircraft to cause far more extensive damage.
The Obama administration is eager to prevent an Israeli attack partly to avoid a major foreign policy crisis during the U.S. presidential campaign and partly because officials say an Israeli strike could set off a new conflagration in the region.
If Iran retaliated by launching missiles at Tel Aviv that killed thousands of Israelis, administration officials say the U.S. would be under enormous pressure to defend Israel and respond, and would then be pulled into another war in the Middle East.