Israel plans to remain ambiguous over its nuclear policy, with US backing, Deputy Foreign Minister Danny Ayalon said on Wednesday.

"This policy of ambiguity constitutes one of the pillars of Israeli national security and the Americans consider it very important," Ayalon told army radio.

"There is no reason for the Americans to change their approach or for Israel to change its position," he said.

For the past four decades, Israeli governments have insisted the Jewish state will not be the first to introduce nuclear weapons in the Middle East.

"This policy will continue and no pressure from any country will make it change, Ayalon said.

But foreign military experts believe Israel has an arsenal of several hundred nuclear weapons.

Ayalon's comments came ahead of next week's nuclear security summit in Washington. Israeli Prime Minister Benjamin Netanyahu will be among the leaders attending the international gathering.

Israel has maintained its policy of deliberate ambiguity about its nuclear programme since it inaugurated its Dimona nuclear reactor in the Negev desert in 1965.

In 1969 it reached an understanding with the United States under which Israeli leaders refrain from making any statement on their country's nuclear potential and do not carry out any nuclear test, while Washington refrains from exerting any pressure on the issue.

The programme is under military censorship.

Like nuclear-armed countries India, Pakistan and North Korea, Israel has not signed the Nuclear Non-Proliferation Treaty in order to avoid inspections by the Vienna-based International Atomic Energy Agency.