WASHINGTON - US Defense Secretary Leon Panetta said that Israel could attack Iran this spring, the Washington Post reported here on Thursday.

The Washington Post story said: "Panetta believes there is a strong likelihood that Israel will strike Iran in April, May or June before Iran enters what Israelis described as a 'zone of immunity' to commence building a nuclear bomb."

The newspaper's columnist David Ignatius wrote in the article that US President Barack Obama and Panetta "are said to have cautioned the Israelis that the United States opposes an attack, believing that it would derail an increasingly successful international economic sanctions program and other non-military efforts to stop Iran from crossing the threshold."

However, the White House hasn't yet decided how the United States would respond if the Israelis do attack, the story added.

The story continued: "US officials see two possible ways to dissuade the Israelis from such an attack: Tehran could finally open serious negotiations for a formula to verifiably guarantee that its nuclear program will remain a civilian one; or the United States could step up its covert actions to degrade the program so much that Israelis would decide that military action wasn't necessary."

The story said that US officials don't think that Israeli Prime Minister Benjamin Netanyahu has made a final decision to attack. But the senior US officials doubt that the Israelis are bluffing, worrying about "the guns of spring - and the unintended consequences."