Israel reacted with anger yesterday to a British news report that it was preparing a pre-emptive nuclear strike against Iran to stop the hardline regime in Tehran from acquiring nuclear weapons.

Sources at the Israeli prime minister’s office, the Foreign Ministry, and the Defense Ministry, as well as a retired intelligence expert, denied the report flatly.

While Israel is unlikely ever to use its nuclear strike capability pre-emptively on Iran, Israeli military planners have long been considering options for conventional strikes if Tehran continues to defy diplomatic pressure.

Prime Minister Olmert prefers to emphasize Israel’s support for the multinational diplomatic effort, although his planners have already spent years considering what to do if the diplomatic track fails.

Israel resorted to force in 1981 to destroy Saddam Hussein’s nuclear reactor at Osirak with conventional bombs dropped from eight F-16 jets in a covert mission known as “Operation Opera.”

Israeli military intelligence accepts that an attack on Iran would be more complex as it presents significant logistic problems for refueling military aircraft. And while most of Saddam’s nuclear program was located in the one Osirak facility, the Iranians have spread theirs to at least a dozen sites, some of which are hidden in tunnel systems built under mountains.

But Israeli military planners still believe a successful bombing raid on a carefully chosen target representing an essential and irreplaceable part of the Iranian program would delay the date for Tehran acquiring nuclear weapons.

Israeli intelligence has altered its estimate for Iran acquiring nuclear weapons after Tehran encountered problems in enriching uranium. The latest estimate puts the date at no earlier than 2010.