The Bush administration was informed in advance and gave the "green light" to Israel's military strikes against Hizbollah ­ with plans drawn up months before two Israeli soldiers were seized ­it has been claimed.

The US reportedly considered Israel's actions as a necessary prerequisite for a possible strike against Iran. A report by a leading investigative reporter says that earlier this summer Israeli officials visited Washington to brief the government on its plan to respond to any Hizbollah provocation and to "find out how much the US would bear".

The officials apparently started their inquiries with Vice-President Dick Cheney, knowing that if they secured his support, obtaining the backing of President Bush and Condoleezza Rice would be easier.

The report by Seymour Hersh quotes an unidentified US government consultant with close ties to the Israelis who says: "The Israelis told us it would be a cheap war with many benefits. Why oppose it? We'll be able to hunt down and bomb missiles, tunnels, and bunkers from the air. It would be a demo for Iran."

A former intelligence officer, also quoted, says: "We told Israel,'Look, if you guys have to go, we're behind you all the way. But we think it should be sooner rather than later. The longer you wait, the less time we have to evaluate and plan for Iran before Bush gets out of office'."

Both Israeli and US officials say that the Israeli military operation against Hizbollah was triggered by the seizing of two Israeli soldiers, apparently to be bargained with for a possible prisoner swap. But Hersh's report, published in today's issue of The New Yorker, adds to evidence that Israel had been anticipating a Hizbollah provocation for some time and planning its response ­ a response that was widely condemned for being disproportionate.

Last month the San Francisco Chronicle reported that "Israel's military response by air, land and sea to what it considered a provocation last week by Hizbollah militants was unfolding according to a plan finalised more than a year ago". The report said that a senior Israeli army officer had been briefing diplomats, journalists and think-tanks for more than a year about the plan and it quoted Gerald Steinberg, professor of political science at [Israel's] Bar-Ilan University, who said: "Of all of Israel's wars since 1948, this was the one for which Israel was most prepared." Last week the New Statesman magazine reported that Britain had also been informed in advance of the military preparations and that the Prime Minister had chosen not to try to stop them "because he did not want to".

This latest report is the first to tie the Israeli operation to a broader framework that includes a possible US strike against Iran.

Unidentified officials said a strike could "ease Israel's security concerns and also serve as a prelude to a potential American pre-emptive attack". Shabtai Shavit, a national security adviser to the Knesset, said: "We do what we think is best for us, and if it happens to meet America's requirements, that's just part of a relationship between two friends. Hizbollah is armed to the teeth and trained in the most advanced technology of guerrilla warfare. It was just a matter of time."

An anonymous Middle East expert claimed that while the State Department supported the plan because it believed it would help the Lebanese government assert control over the south, the White House was focussed on stripping Hizbollah of its missiles.

The expert added: "If there was to be a military option against Iran's nuclear facilities, it had to get rid of the weapons that Hizbollah could use in a potential retaliation at Israel. Bush was going after Iran, as part of the 'axis of evil', and its nuclear sites, and he was interested in going after Hizbollah as part of his interest in democratisation."

Last night the White House denied the allegations contained in Hersh's piece with a brief statement from the President describing it as "patently untrue". Mr Bush's national security adviser, Stephen Hadley, added: " The suggestion that the US and Israel planned and co-ordinated an attack on Hizbollah ­ and did so as a prelude to an attack on Iran ­ is just flat wrong."