British Foreign Secretary Philip Hammond on Thursday sought to reassure Israel over a nuclear deal between major powers and Iran, saying "robust measures" were in place to ensure its success.

Israel has long opposed any deal with its arch-foe Iran, and Prime Minister Benjamin Netanyahu lambasted the landmark agreement struck Tuesday between Tehran and six world powers as a "historic mistake".

"We would not have agreed to the deal unless we were sure we had robust measures in place to deliver effective oversight of Iran's nuclear programme," Hammond said ahead of a meeting with Netanyahu in Jerusalem.

"Our focus now will be on swift and full implementation of the agreement to make sure that a nuclear weapon remains beyond Iran's reach."

Hammond was the first senior official from the so-called P5+1 countries to visit Israel since the deal to rein in Iran's atomic programme in return for relief from crippling economic sanctions.

The P5+1 -- the United States, Russia, Britain, China, France and Germany -- inked the agreement in Vienna after months of intense diplomacy.

The international community charges that Iran's nuclear programme has been aimed at producing an atomic bomb, which Tehran denies, insisting its facilities are for civilian use only.

Under the 10-year deal, Iran is to reduce stockpiles of enriched uranium and slash the number of centrifuges it runs, which can make fuel for nuclear power.

Israel immediately denounced the agreement, with Netanyahu calling it a "historic mistake" and saying it would provide billions of dollars of relief that Iran would funnel into arming proxy militants in the Middle East.

The Jewish state has threatened to use military force to prevent Iran obtaining nuclear weapons capability, and has long opposed any deal with Tehran.

- Fundamental disagreement -

Netanyahu insists Israel would not be bound by the deal and signalled military force is not off the table.

On Wednesday, he declared the agreement was "not the end of the story".

Responding to the icy response, Hammond said: "Prime minister, I know that you disagree fundamentally with the way we have approached this issue.

"Let me be clear -- you said we will lift the sanctions today. We will not lift any sanctions today. All of the sanctions relief in this agreement is conditional upon Iran having first met the requirements on it to reduce its stockpiles, to dismantle centrifuges, to export its stocks of enriched uranium."

Iran will remain under the threat of renewed international sanctions for 15 years, according to a letter to the UN from the P5+1.

The accord also features a "snapback" mechanism to restore the sanctions almost immediately if Iran does not live up to its commitments.

Hammond said Wednesday there was no agreement that the powers could have struck with Iran that would have been acceptable to Israel, saying the Jewish state wanted a "permanent state of standoff" with Tehran.

Netanyahu is expected now to lobby the US Congress, which has 60 days to review the deal.

He has allies there, particularly among Republicans, but their chances of sinking the agreement appear unlikely for now.

Israel is believed to be the only country in the Middle East with atomic bombs, although it has never confirmed it.