The head of the UN's nuclear watchdog, Mohamed ElBaradei, says Israel should start discussions on ridding the Middle East of nuclear weapons.
Mr ElBaradei wants discussions to begin before any peace deals
He said such dialogue would help reduce frustration in the region about "what is seen to be a widespread imbalance".
Mr ElBaradei is scheduled to travel to Israel next month to discuss making the Middle East a nuclear-free zone.
He said everyone knew that Israel had a nuclear capability - even if Israel has always refused to admit it.
"We need... to rid the Middle East of all weapons of mass destruction," he told Reuters news agency on a visit to Russia.
"Israel agrees with that, but they say it has to be... after peace agreements.
"My proposal is may be we need to start to have a parallel dialogue on security at the same time when we're working on the peace process."
Mr ElBaradei said he would like Israel, along with other Middle East countries, to open up nuclear facilities to inspections by the UN's International Atomic Energy Agency.
But he would not be insisting Israel admits to having nuclear weapons, when he visits the country in early July.
"I think everybody takes it as a given that Israel has a nuclear capability, if not nuclear weapons," he said.
"So whether they would like to come in the open, whether they maintain... ambiguity, it's for them to decide."
Israel has a policy of "strategic ambiguity" - neither admitting nor denying it has nuclear weapons - but analysts believe it has more than 100 nuclear weapons.
Its Arab neighbours have frequently accused the international community of double standards for requiring them to be free of nuclear weapons while doing little, in their eyes, about Israel.
Mr ElBaradei said it was "not sustainable in any region or even globally to have some [people] rely on nuclear weapons and others being told they should not have nuclear weapons".