Iran's nuclear programme has been beset by difficulties, leaving Tehran still about three years away from being able to build nuclear weapons, Israel's strategic affairs minister said on Wednesday.

"The Iranian nuclear programme has a number of technological challenges and difficulties, so it has not succeeded," Moshe Yaalon, who is also a former Israeli military chief, told public radio.

He did not spell out the problems affecting the Iranian programme or claim any Israeli involvement.

However, there has been widespread speculation that Israel was behind the Stuxnet worm that has attacked computers in Iran, and Tehran has blamed Israel and the United States for the killing of two nuclear scientists in November and January.

"These difficulties have postponed the timetable," said Yaalon. So we can't talk about a point of no return. Iran does not have the ability to create nuclear weapons by itself at the moment."

He said Tehran now appeared to be about three years away from being able to produce the bomb.

"It is likely to happen in the next three years, if it is successful. And I hope it will not be successful at all and that the efforts of the West will prevent Iran from developing a nuclear capability," Yaalon said.

Israel, which has the Middle East's sole if undeclared nuclear arsenal, regards Iran as its principal threat, after repeated predictions by the Islamic republic's hardline President Mahmoud Ahmadinejad of the Jewish state's demise.

Along with the West, Israel suspects Iran of trying to develop atomic weapons under the guise of a civilian nuclear programme, a claim Tehran denies.

Israel has backed US-led efforts to prevent Iran from developing a nuclear weapons capability through sanctions, but has also refused to rule out military force.