By Dan Williams
JERUSALEM (Reuters) - Defense Minister Ehud Barak played down speculation on Saturday that Israel and U.S.-led allies were waging clandestine war on Iran, saying sanctions and the threat of military strikes were still the way to curb its nuclear program.
Barak was asked in an interview whether two explosions in Iran last month showed "the war has already begun" through sabotage.
"I don't think so," he told Channel Two television. "I think that the answer to your question is negative."
One of last month's explosions in Iran killed at least a dozen members of the Revolutionary Guards, including a general. Iran called it an accident that occurred while weapons were being moved.
The Iranians have suffered from computer viruses in industrial systems. Several nuclear scientists have been killed or disappeared over the years in what Tehran says were Israeli or U.S. covert operations.
The idea that such operations may have escalated to include spectacular blasts with double-digit death tolls has stirred concern in Israel, where some commentators warned of a possible spillover into reprisals by Iran or its sympathizers abroad.
Barak neither confirmed nor denied that Israel or Western powers were trying to delay Iran's uranium enrichment and missile programs through sabotage. But his remarks signaled doubt in the long-term efficacy of any such tactics.
"I have nothing to say about the actions themselves. I just say that if you compare the situation eight years ago, or four years ago, to today's situation, the Iranians are much closer to nuclear capability," he said.
"Therefore the sanctions have to be intensified, quick, determined ... and therefore everyone is saying that no option should be taken off the table," Barak added, using a phrase favored by Israel and the United States to show they consider military strikes on Iran's nuclear sites a last-ditch option.
Barak said Israel and the United States were coordinating closely on Iran, which denies seeking nuclear weapons and has vowed to retaliate for any preemptive attack.
But the Jewish state has sovereignty and ultimate responsibility for its security, Barak added - comments that, in the past, have been widely interpreted as a threat to strike Iran unilaterally if the Israelis deems diplomacy a dead end.
On Friday, U.S. Defense Secretary Leon Panetta used some of his strongest language yet to explain why Washington is wary of the consequences of any such action.
Addressing a pro-Israel forum in Washington, Panetta said an attack could disrupt the already fragile economies of Europe and the United States, trigger Iranian retaliation against U.S. forces, and ultimately spark a popular backlash in Iran that would bolster its rulers.
It also may not be effective. Panetta cited estimates from the Israelis that a military strike might set back Iran's nuclear program by one to two years "at best."
Iran has weathered several rounds of sanctions passed by the U.N. Security Council and Western powers. A U.N. watchdog report last month suggested Iran has worked on a nuclear bomb program, heightening the international pressure.
(Writing by Dan Williams; Editing by Peter Graff)