JERUSALEM - Officials are quietly conceding that new international sanctions targeting Iran's suspect nuclear program, while welcome, are further constraining Israel's ability to take military action just as a window of opportunity is closing because Tehran is moving more of its installations underground.
The officials say that Israel must act by the summer if it wants to effectively attack Iran's program.
A key question in the debate is how much damage Israel, or anyone else, can inflict, and whether it would be worth the risk of a possible counterstrike.
Israel has been a leading voice in the international calls to curb Iran's nuclear program. Like the West, it believes the Iranians are moving toward nuclear weapons capability a charge Tehran denies.
Israel contends a nuclear-armed Iran would threaten its survival, citing Tehran's calls for the destruction of the Jewish state and its support for anti-Israel militant groups. It also fears an Iranian bomb would touch off a nuclear arms race in a region still largely hostile to Israel.
Israeli leaders say they prefer a diplomatic solution. But skeptical of international resolve Israel refuses to rule out the use of force, saying frequently that "all options are on the table."
In comments Friday to the World Economic Forum in Davos, Switzerland, Israeli Defense Minister Ehud Barak called for even tougher sanctions against Iran and said time was running out for the world to act.
"We are determined to prevent Iran from turning nuclear," he said. "It seems to us to be urgent, because the Iranians are deliberately drifting into what we call an immunity zone where practically no surgical operation could block them."
Returning Monday to Israel, Barak added: "We must not waste time on this matter; the Iranians continue to advance (toward nuclear weapons), identifying every crack and squeezing through. Time is urgently running out."
Key Israeli defense officials believe that the time to strike, if such a decision is made, would have to be by the middle of this year.
Complicating the task is the assessment that Iran is stepping up efforts to move its work on enriching uranium a critical component of bombmaking deep underground. Iran's enrichment site at Fordo near the Iranian city of Qom, for instance, is shielded by about 300 feet (90 meters) of rock.
A team of U.N. nuclear inspectors, including senior weapons experts, is in Iran this week, and the findings from the visit could greatly influence Western efforts to expand economic pressures on Tehran over its uranium enrichment.
The European Union this month decided to stop importing oil from Iran just weeks after the U.S. approved, but has yet to enact, new sanctions targeting Iran's Central Bank and, by extension, its ability to sell its oil.
Several officials at the heart of the decision-making structure, speaking on condition of anonymity because they were discussing some of Israel's deepest secrets, said they feel compelled to give the sanctions time.
In this way, somewhat paradoxically, the new economic sanctions the U.S. and Europe are imposing while meeting a repeated Israeli request have emerged as an obstacle to military action.
An Israeli strike would risk shattering the U.S.-led diplomatic front that has imposed four additional rounds of sanctions on Iran and jolt the shaky world economy by causing oil prices to spike. Still, officials say, if Israel feels no alternative but to take military action, it will do so.
Israel possesses dozens of F-16s and F-15s, some customized with long-range fuel tanks, and has bought additional Dolphin submarines from Germany capable of firing nuclear missiles.
It introduced a fleet of huge pilotless planes known as Heron TPs that can reach the Persian Gulf, provide surveillance and be used for aerial refueling likely a critical aspect of any Iran mission. One of the Herons, which are the size of Boeing 737s, crashed during a test flight Sunday.
The U.S. has sold Israel dozens of 100 GBU-28 laser-guided "bunker-buster" bombs. The 2.5-ton bombs are capable of penetrating more than 20 feet (6 meters) of solid concrete.
It's not clear how much damage the bunker-busters could actually do. Iran's main enrichment site at Natanz is believed to be about 25 feet (6 meters) underground and protected by two concrete walls.
U.S. Defense Secretary Leon Panetta told The Wall Street Journal last week that even more sophisticated U.S. bunker-busters aren't powerful enough to penetrate all of Iran's defenses.
While the rewards of an attack are uncertain, the risks are great.
Many believe Iran would likely unleash its large arsenal of missiles capable of striking Israel and its local proxies, Hezbollah to Israel's north and Hamas to the south, possess tens of thousands of short-range rockets and missiles. American soldiers in the Persian Gulf might come under fire. Islamist backers of Iran could target civilians all over the world.
The prospect of a new conflagration in the Mideast is one reason cited by some influential Israeli figures, like recently retired spy chief Meir Dagan, when arguing against an Israeli military attack.
But that view is beginning to be challenged. In a radio interview several weeks ago, Barak played down the risk of Iranian missiles, saying casualties would be limited.
Perhaps the biggest factor in the Israeli thinking is how much damage an airstrike could even cause.
"What will tip the scales in favor or against an attack is whether we will really be able to do inflict serious damage," said Yiftah Shapir, an expert in nuclear arms proliferation at Tel Aviv University. "That will be more important than whether we are ready to absorb (the casualties) of an attack."
"If you are talking about the use of power against Iran, any kind of power, and create any damage over there, yes, it can be done," a senior Israeli military official told The Associated Press, speaking on condition of anonymity under military guidelines.
Israel has a history of taking action against perceived nuclear threats. In 1981, it destroyed an unfinished Iraqi nuclear reactor, and in 2007, it struck what is believed to be a nuclear reactor in Syria.
An Iranian mission would be far more complicated.
Israeli officials believe the Iranian nuclear program is so far advanced that any attack would delay it by two to three years at best, but not destroy it.
And unlike the Iraqi and Syrian targets, Iran has spread out its nuclear targets across the country and buried the installations deep underground. This has created a huge logistical challenge.
"It's a very advanced program with many facilities, some very large and some very fortified. To destroy them you need a series of massive assaults for two to three weeks, a month, something like that," Shapir said.
A one-time surgical strike, the most likely attack by Israel, "can't do more than politically declare that we aren't willing to tolerate" a nuclear Iran, Shapir said.
That has raised speculation that Israel's veiled threats are no more than attempts to get Iran to back down.
Israeli warplanes would have to travel 1,000 miles (1,600 kilometers) to reach Tehran. This would mean crossing through potentially hostile Arab airspace and could require warplanes to refuel along the way, a time-consuming process that could leave aircraft vulnerable.
There are other options. Israel has been widely blamed for a computer virus that attacked Iranian centrifuges, sophisticated equipment needed to enrich uranium, as well as the mysterious assassinations of Iranian nuclear scientists. Israel has never confirmed involvement, and Israeli cyberexperts say such activities are unlikely to deliver the program a major blow.
Israeli officials have also floated other scenarios, such as crippling Iranian ports or oil fields.
Israel clearly prefers the U.S. to lead any military operation against Iran, in which case Israel would presumably commit, as it did in the 1991 Gulf War, to act in coordination with the U.S. and operate missile defense systems.
Israeli defense officials estimate that because of its superior firepower, the U.S. could wait until next year and still have the capability to act.
U.S. military and political officials have spoken out in the past against an Israeli attack. Israeli defense officials say they haven't committed to giving the U.S. significant notice of an Israeli airstrike.
But the U.S. and Israel are working together on projects to improve combat jet range, communications and refueling. They also share intelligence reports and are jointly developing missile defense systems.