Israeli Prime Minister Benjamin Netanyahu has denied accusations he is interfering in the US presidential vote by pushing President Barack Obama to take a tougher stand on Iran's nuclear programme.

In newspaper interviews published on Friday ahead of the Jewish new year, Netanyahu dismissed accusations that he is trying to paint Obama as weak on Iran in order to boost support for Republican candidate Mitt Romney.

"That's nonsense," he told the Israel Hayom daily, which is considered close to him.

"The issue that guides me is not the elections in the United States but the centrifuges in Iran. What can we do if the centrifuges in Iran pay no attention to the political timetable in the United States?"

"It has nothing to do with the American elections," he added, in an interview with the Jerusalem Post newspaper.

"If the centrifuges stop miraculously, if they stop preparing enriched uranium to make atomic bombs, then I suppose I wouldn't have to speak out.

"For me this is a policy issue, a security issue, and not a political issue," he said.

The comments are excerpts from longer interviews to be published in full on Sunday, the eve of the Jewish new year, or Rosh Hashana.

Opposition leader Shaul Mofaz on Wednesday said that Netanyahu's pursuit of a very public dispute with Obama over Iran was an attempt to sway voters against the US leader in the November election.

"Israeli meddling in internal US affairs and turning the US administration from an ally to 'an enemy' has caused us severe damage," Mofaz charged, at a session of the Israeli parliament, known as the Knesset.

"Please explain to us: who is Israel's greatest enemy -- the US or Iran? Who do you fear more -- (Iranian President Mahmoud) Ahmadinejad or Obama? Which regime is more important to overthrow -- the one in Washington, or in Tehran?" he asked.

Similar criticism has been expressed by Israeli and US media over Netanyahu's repeated demands that Obama set unambiguous 'red lines' with regard to Iran's nuclear programme, which Israel and much of the West believes masks a weapons drive.

Israel, the Middle East's sole, if undeclared, nuclear power, has said a nuclear-armed Iran would pose an existential threat to the Jewish state and has threatened unilateral military action against Tehran.

But Washington backs continued diplomatic pressure and says it is not the time for a strike.

"The president has said unequivocally he will not allow Iran to obtain a nuclear weapon," State Department spokeswoman Victoria Nuland told reporters on Monday, but Netanyahu still appears unconvinced.

"I hear those who say we should wait until the last minute," he said in the Israel Hayom interview. "But what if the United States does not act? That is a question that must be asked.

"You can defend against missiles one way or another but there is something against which there is no defence: The atom," he added.

"The only defence is to prevent creation of such a reality by your enemy, and of course make it clear to anyone who would consider ever attacking Israel with weapons of mass destruction that the consequences will be on his own head."