"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.

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

Foreign military experts believe Israel has an arsenal of several hundred nuclear bombs.

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.

Israel is not a signatory to the nuclear Non-Proliferation Treaty and has said it will not sign up for a Middle East nuclear-free zone being promoted by the United States.

Israel's nuclear whistleblower Mordechai Vanunu was jailed in 1986 for disclosing the inner workings of Israel's Dimona nuclear plant to Britain's The Sunday Times newspaper.

Since his release in 2004, he has been detained several times for violating the terms of his parole which ban him from travel or contact with foreigners.

Avner Cohen, author of the revelatory Israel and the Bomb, which has drawn upon thousands of documents and tens of interviews on the Israeli nuclear firepower, had said a recent US-Israeli accord amounted to "the United States passively accepting Israel's nuclear weapons status as long as Israel does not unveil publicly its capability or test a weapon."