The UN Security Council unanimously adopted a resolution Monday endorsing the historic deal on Iran's nuclear program and cleared a path to lift sanctions crippling its economy.

It marks formal UN approval for the hard-won, groundbreaking agreement reached between Tehran and the five permanent members of the Security Council plus Germany, after 18 straight days of talks that capped almost two years of momentous negotiations.

The passing of the resolution sets in motion a gradual process -- conditional on Iran abiding by the deal -- that can terminate seven UN resolutions imposing sanctions on Iran since 2006.

The agreement with Tehran was reached on Tuesday in Vienna by the UN council's five permanent members -- Britain, China, France, Russia and the United States, plus Germany.

US President Barack Obama said he hoped the resolution would "send a clear message" that diplomacy is "by far our strongest approach to ensuring that Iran does not get a nuclear weapon."

Faced with the prospect of Iranian oil returning to the global market, crude prices fell for a fourth straight session, dropping to $50.15 a barrel on the New York Mercantile Exchange.

In the Security Council, ambassadors said the years of hard work on Iran should become a blueprint for how the world deals with other crises such as those in Syria and Yemen.

"When our nations truly unite to confront global crises, our influence grows exponentially," said US envoy Samantha Power.

"It should motivate us to do far more."

Russian ambassador Vitaly Churkin said: "We turn not simply a page but a whole chapter in the work of the Council by creating a new reality."

- Iran 'ready to engage' -

The deal has been touted as an opening for greater contact between Iran and the leading nations in other areas, especially on tackling the Islamic State group in Iraq and Syria.

Iranian envoy Gholamali Khoshroo said that Tehran was ready "to engage in good faith" with its neighbors in the region.

"This is the time to start working together against our most common and important challenges, which include above all violent extremism," he said.

But Israel continues to reject the deal. On Monday, the Gulf Cooperation Council also protested "contradictory" signals coming from Iran since its struck the accord.

US Defense Secretary Ashton Carter visited Israel in a bid to ease concerns, signaling Washington was ready to boost military cooperation with the Jewish state.

Prime Minister Benjamin Netanyahu maintains that there is not enough in the deal to prevent the Islamic republic from obtaining nuclear weapons that could be used to target Israel.

"Today you have awarded a great prize to the most dangerous country in the world," Israeli ambassador to the United Nations Ron Prosor said after the vote.

The resolution charges the UN nuclear watchdog, the International Atomic Energy Agency, to "undertake the necessary verification and monitoring of Iran's nuclear commitments."

Those commitments include limiting the number of centrifuges for its fissile material. The resolution demands that Iran "cooperate fully" with the IAEA.

- Sanctions threat stays for 15 years -

As soon as the council receives IAEA confirmation that the nuclear program is entirely peaceful, the seven UN sanctions resolutions against Tehran will be terminated and replaced by the terms of Monday's resolution.

Sanctions to be lifted include a ban on the trade of goods or services linked to Iranian nuclear activities, and the freezing of financial assets of designated Iranian officials and companies.

But embargoes on the sales and exports of conventional weapons and ballistic missile technology will remain in place -- for five years for conventional weapons and for eight years for missile technology.

If Tehran violates any of its commitments, the council can initiate proceedings to reinstate its panoply of sanctions.

The so-called "snapback" mechanism can put old sanctions back in place if world powers feel Iran has not met its commitments under the Vienna deal.

It leaves Iran under the threat of renewed sanctions for 15 years -- 10 under the Vienna agreement endorsed by the UN, and the P5+1 committing to another five years of tight monitoring.

In the United States, a Republican-majority Congress has 60 days to review the deal.

The Congress can pass a motion of disapproval, but President Barack Obama can then veto that. An override of the veto requires two-thirds approval in both the House and Senate.