ROME: Israel's prime minister urged the US on Wednesday to be as tough in nuclear negotiations with Iran as it is about dismantling Syria's chemical weapons stockpile.

The comments put new pressure on Washington to convince two of its key Mideast allies that America will not sell out their interests as it tentatively warms diplomacy with Tehran.

Prime Minister Benjamin Netanyahu, at the start of a seven-hour meeting with US Secretary of State John Kerry, said the world should not accept what he called a ''partial deal'' with Iran.

He said that would include any agreement that falls short of requiring Iran to end all enrichment on uranium, get rid of all fissile material, and close water plants and underground bunkers that he said are only necessary to build a nuclear bomb.

Negotiations between Iran and world powers, which resumed several weeks ago after a six-month lull, have come nowhere near demanding the level of tough restrictions on Tehran that Israel wants.

The nuclear talks also have spooked Saudi Arabia, spurring Kerry to meet with top officials from both Mideast nations about an issue that has unified the two longtime adversaries.

Iran maintains that its nuclear program is peaceful, and its capabilities necessary for energy and medical uses.

''A partial deal that leaves Iran with these capabilities is a bad deal,'' Netanyahu told Kerry at the start of their meeting in Rome. ''You wisely insisted there wouldn't be a partial deal with Syria. You're right. If (Syrian President Bashar) Assad had said, 'Well, I'd like to keep, I don't know, 20 per cent, 50 per cent, or 80 per cent of my chemical weapons capability,' you would have refused, and correctly so.''

Netanyahu also said the US should retain its harsh economic sanctions against Iran until it dismantles its nuclear program.

''That's what got them into these renewed negotiations in the first place,'' he said.

Obama administration officials are weighing whether to ease some sanctions, even as some US lawmakers in Congress are eyeing plans to tighten the economic hurdles, if Iran takes steps to scale back its program.

Kerry, who spent the last three days in meetings with European and Mideast officials that focused mostly on Iran and Syria, said the U.S. would continue to do everything it can to prevent Tehran from building nuclear weapons. But he stopped short of agreeing with Netanyahu's demands.

''We will need to know that actions are being taken which make it crystal clear, undeniably clear, failsafe to the world, that whatever (Iranian) program is pursued is indeed a peaceful program,'' Kerry said. ''No deal is better than a bad deal. But if this can be solved satisfactorily, diplomatically, it is clearly better for everyone.''

Neither Israel nor Saudi Arabia has been included in the world powers' negotiations with Iran.

Senior Saudi officials this week described a widening gulf between Washington and Riyadh over US policy in Iran and Syria.

Saudi Arabia also wants the US to send more military support to opposition groups seeking to oust Assad from power as an end to Syria's civil war that has killed more than 100,000 people.

The Iranian government has been the key benefactor to Assad, and has sent military forces, weapons and funding to support his government against the rebellion.

Both the US and Saudi Arabia are working to start talks between Assad and opposition leaders to create a new government in Syria that, ultimately, would not include Assad.

Syrian National Coalition President Ahmad al-Jarba on Tuesday told reporters in London that he was not ready to agree to the negotiations, but opposition officials will vote on whether to participate in coming days.

The impasse over the Syrian negotiations comes as a team of inspectors with the United Nations and the Organisation for the Prohibition of Chemical Weapons work to dismantle Assad's chemical weapons stockpile, which is considered one of the world's largest, after a deadly Aug 21 chemical weapons attack.

Kerry met with Saudi Foreign Minister Prince Saud al-Faisal in Paris on Monday in what he described as a ''delightful and very, very constructive'' discussion.

He brushed off suggestions of diplomatic chilliness between the two nations.

On Iran, ''I think they understand exactly what the United States is engaged in,'' Kerry said a day later in London when asked about tensions between Washington and Riyadh. ''And I reiterated our position in any negotiation that our eyes are wide open, actions are what will speak to us, not words.''

In Rome, Kerry and Netanyahu also discussed ongoing peace talks between Israel and Palestinian authorities who were meeting in Jerusalem even as officials warned about threats that would rise in the event of a stalemate.

Netanyahu said any agreement must result in ''a peace that Israel can defend by itself, for itself against any conceivable threat.''

He called the creation of a Palestinian state ''a fundament for any peace.''