
The Israeli security establishment is divided over whether it needs  Washington's blessing if Israel decides to attack Iran, Israeli officials say,  as the U.S. campaign for sanctions drags on and Tehran steadily develops greater  nuclear capability.
Some senior Israeli officials say in interviews that  they see signs Washington may be willing to live with a nuclear-armed Iran, an  eventuality that Israel says it won't accept. Compounding Israeli concerns were  U.S. statements this past weekend that underscored U.S. resistance to a military  option. Defense Secretary Robert Gates on Sunday discussed a memo to National  Security Adviser James Jones warning that the U.S. needed new strategies,  including how to contain a nuclear Iran—suggesting that Iran could reach nuclear  capability without any foreign military force trying to stop it. 
Adm.  Mike Mullen, chairman of the Joint Chiefs of Staff, reiterated Sunday the U.S.  position that a military strike against Iran is a "last option."
Israel  says it supports the U.S.-led push for new economic sanctions against Iran. But  Israeli officials have increasingly voiced frustration over the slow pace of  diplomatic efforts to get sanctions in place. 
Relations between the two  allies have soured in recent weeks, with Prime Minister Benjamin Netanyahu's  government pushing back against Obama administration pressure to freeze building  in Jewish areas of East Jerusalem, which Washington says is counterproductive to  its Mideast peace efforts. 
In another sign of a split, Israeli officials  say they believe Iran—whose president has called for the destruction of  Israel—could develop a warhead to strike the country within a year if it decides  to, though outside experts say such capability is years away. Tehran says its  nuclear program is for peaceful uses.
Such divisions have played into  fears in Israel that if Washington's sanctions effort fails, the Israeli and  American positions on Iran could rapidly diverge—and Israel, if it chooses to  attack Iran, would have no choice but to do so on its own.
U.S.  commanders say an attack would invite retaliation by Iran against American  military interests in the region, or wider terrorist attacks by Iranian proxies  Hezbollah and Hamas. Adm. Mullen said Sunday a strike could have "unintended  consequences," and has long warned it could destabilize the region at a time the  U.S. has troops in Iraq and Afghanistan, which neighbor Iran. 
A senior  U.S. official said the U.S. has stated to Israel its opposition to unilateral  Israeli action, but that there were still fears within the administration that  Israel could strike Iran despite Washington's objections.
If Israel  chooses to attack nuclear facilities in Iran against Washington's objections,  politics will play a role in military strategy.
Some Israeli officials  worry a unilateral strike would cause a break with Washington that would  threaten Israeli national interests even more than a nuclear-armed  Iran.
Israel's track record of coordinating such strikes with the U.S. is  mixed. The country caught the U.S. by surprise with its attack on Iraq's Osirak  reactor in 1981. When Israel attacked a suspected Syrian nuclear facility in  2007, Washington was given advanced warning, according to U.S. officials at the  time.
The decision of whether to strike Iran ultimately rests with the  prime minister, Mr. Netanyahu. In the past, however, senior military commanders  have had significant say in such decisions. A spokesman for Israel's Ministry of  Defense declined to comment on internal deliberations concerning  Iran.
There are a number of routes Israeli attack jets can fly to attack  Iran. They all would require Israeli planes to fly through U.S.-controlled  airspace in Iraq or through the airspace of U.S. allies such as Saudi Arabia or  Turkey, which could cause serious political consequences for Israel.
Many  Israeli military experts say Israel can easily cope with any military  retaliation by Iran in response to a strike. Iran's medium-range rockets would  cause damage and casualties in Israel, but they aren't very accurate, and  Israel's sophisticated missile-defense system would likely knock many out  midflight. Israel has similarly proved it can handle attacks against Israel by  Hezbollah and Hamas. Israel also hosts a contingent of U.S. troops attached to a  radar system to help give early warning against incoming rocket  attacks.
More worrying to Israeli strategic planners examining possible  attack scenarios is the possibility that Iran would respond to an Israeli attack  by ramping up support to groups battling U.S. troops in Iraq and Afghanistan,  according to recently retired officials familiar with the military's thinking on  Iran. If American soldiers start dying in greater numbers as a result of an  Israeli unilateral attack, Americans could turn against Israel. 
Iran  could also disrupt the world's oil supply by cutting off exports through the  Persian Gulf, roiling international oil markets.
"What will Americans say  if Israel drags the U.S. into a war it didn't want, or when they are suddenly  paying $10 a gallon for gasoline and Israel is the reason for it," says retired  Brig. Gen. Shlomo Brom, former director of the Israeli army's Strategic Planning  Division.
Former senior members of Israel's defense establishment have  weighed in recently on both sides of the debate.
"We don't have  permission and we don't need permission from the U.S.," says Ephraim Sneh, who  served as deputy minister of defense under former Prime Minister Ehud Olmert.  But Maj. Gen. Giora Eiland, a former national security adviser, says Israel  wouldn't jeopardize its relationship with the U.S. by launching a military  strike against Iran without an American nod. 
Late last month, Israeli  Defense Minister Ehud Barak seemed to acknowledge publicly the opposing  viewpoints inside the administration.
"Only we have the exclusive  responsibility when it comes to the fate and security of Israel, and only we can  determine the matters pertaining to the fate of Israel and the Jewish people,"  Mr. Barak said. "But we must never lose sight of how important these relations  are, or the ability to act in harmony and unity with the United States."