Nation & World

JERUSALEM — Israeli leaders on Thursday delivered one of the bluntest warnings to date of possible airstrikes against Iranian nuclear sites, adding to the anxiety in Western capitals that a surprise attack by Israel could spark a broader military conflict in the Middle East.

Defense Minister Ehud Barak, speaking at a security forum attended by some of Israel's top intelligence and military leaders, said time was running out for stopping Iran's nuclear advance, as the country's uranium facilities disappear into newly constructed mountain bunkers.

"Whoever says 'later' may find that later is too late," Barak said. He switched from Hebrew to English for the last phrase: "later is too late."

The language reflected a deepening rift between Israeli and U.S. officials over the urgency of stopping Iran's nuclear program, which Western intelligence officials and nuclear experts say could soon put nuclear weapons within the reach of Iran's rulers.

Although accepting the gravity of the Iranian threat, U.S. officials fear being blindsided by an Israeli strike that could have widespread economic and security implications and might only delay, not end, Iran's nuclear pursuits.

In a series of private meetings with Israeli counterparts in recent weeks, Western officials have counseled patience, saying recent economic sanctions and a new European oil embargo are pummeling Iran's economy and could soon force the country's leaders to abandon the nuclear program. Yet Israelis are increasingly signaling that they may act unilaterally if there is no breakthrough in the coming months, according to current and former administration and intelligence officials.

Defense Secretary Leon Panetta is one of several administration officials to express concern publicly that Israel is positioning itself for a surprise attack.

"Israel has indicated they're considering this, and we have indicated our concerns," Panetta said Thursday after a NATO meeting in Brussels. He declined to comment on published reports that he thinks the Israelis could carry out a strike this spring, possibly as early as April.

Although the Obama administration has not ruled out U.S. military action against Iran, officials are worried that a unilateral strike could shatter the broad international coalition assembled in the past three years to confront Iran over its nuclear program, which Iranian leaders have consistently said is for peaceful purposes.

U.S. officials fear that an attack by Israel could trigger Iranian retaliation against the Jewish state and against U.S. interests around the world.

Administration officials have hinted that the United States might not intervene militarily in a hostile exchange between Israel and Iran unless the conflict began to threaten U.S. forces or Israeli population centers. In an interview last month on CBS' "60 Minutes," Panetta said that in the event of an Israeli strike, U.S. military officials' primary concern would be "to protect our forces."

British Deputy Prime Minister Nick Clegg also expressed concern Thursday that Israel was moving closer to a decision on a potentially destabilizing military strike. "Of course I worry that there will be a military conflict and that certain countries might seek to take matters into their own hands," Clegg told the House magazine, a weekly British political journal.

Clegg, whose government recently imposed new sanctions against Iran's central bank, said Britain was convinced that, "There are very tough things we can do which are not military steps in order to place pressure on Iran."

At Thursday's Israeli security conference, in the resort city of Herzliya, Barak and other Israeli officials pointed to recent moves by Iran to begin enriching uranium at a second plant, located in a bunker built into a mountain near the city of Qom. Once that facility is complete, deterring Iran will be far more difficult, they say.

Barak rejected criticism that Israeli leaders had failed to consider the full implications of a military action. "There is no basis for the claim that this subject ... was not discussed with appropriate breadth and depth," he said.

Post staff writers Craig Whitlock and Karen DeYoung contributed to this report.