US allies in the Gulf have backed the nuclear deal with Iran, after the US promised them better intelligence-sharing and faster arms transfers.
Qatari Foreign Minister Khalid al-Attiya said the Iran deal represented the best option for regional stability.
He was speaking after talks with visiting US Secretary of State John Kerry, who is trying to win support for the deal in the Sunni-dominated Gulf.
Gulf states accuse Shia Iran of stoking unrest in Syria, Iraq, and Yemen.
They fear the nuclear deal will encourage the Tehran government to boost support for proxies who are fighting Sunni forces across the region.
The US has argued that the deal, aimed at preventing Iran from gaining a nuclear weapon in exchange for sanctions relief, will make the region safer.
On Monday, Mr Kerry discussed the nuclear deal with members of the Gulf Co-operation Council (GCC) – a regional body bringing together Saudi Arabia, the United Arab Emirates, Kuwait, Oman, Bahrain and Qatar.
He later told reporters “it was crystal clear that the US and GCC” regarded their partnership “as indispensible for the security of the region”.
He said the US had agreed to speed up the transfer of weapons – including missiles – to its allies in the Gulf, as well as to co-operate more closely with them against Islamic State (IS) militants and al-Qaeda.
Analysis: BBC Security Correspondent Frank Gardner
The main topic of Monday’s talks has been the US effort to allay Arab concerns over the 14 July nuclear deal with Iran. Saudi Arabia and its closest allies fear that the deal will make it more, not less, likely, that Tehran will eventually build a nuclear bomb.
A separate trilateral meeting between the US, Russian and Saudi foreign ministers has been focusing on Syria. But Gulf Arab governments also have mounting security concerns closer to home.
Despite being the most prosperous and stable part of the Arab world, the six Gulf Arab states now find themselves facing a twin threat of domestic terrorist attacks from two ideologically opposed foes: Sunni and Shia extremists.
Read more: Gulf Arabs face twin terror threats
A good deal, for now?
Mr Attiya said he welcomed the nuclear deal as “the best option among other options”.
“We are sure all efforts exerted make this region very stable, very secure,” he said.
He also echoed Mr Kerry’s comments on Syria, emphasising the need for a political solution to the conflict between rebel groups and the government of President Bashar al-Assad.
Speaking earlier in Cairo, Mr Kerry acknowledged regional concerns over the nuclear deal – but insisted it would lessen the threat from Iran.
“If Iran is destabilising, it is far, far better to have an Iran that doesn’t have a nuclear weapon than one that does,” he told reporters.
The deal was reached in Vienna in July after marathon talks between Iran and six world powers, including the US and Russia.
The agreement envisages lifting economic sanctions in exchange for curbs on Iranian nuclear activity, which are intended to stop the country from developing a bomb. Iran has always insisted that its nuclear work is peaceful.
While in Doha, Mr Kerry is also due to meet foreign ministers from Saudi Arabia and Russia to discuss the conflict involving IS in Syria.
Russia and Iran are allied with Syrian President Bashar al-Assad, while the Saudi government and the US have called for him to leave office.
However, all sides are opposed to IS, which has emerged as a major player in Syria’s civil war.
On Monday, a Kremlin spokesman criticised US plans to provide air cover for Syrian rebel groups fighting President Assad’s forces, as well as those fighting IS.
“Helping Syrian opposition, let alone helping with financial or technical means, would lead to a further destabilisation of the situation in the country,” Dmitry Peskov told reporters.
The US, working alongside Turkey, is hoping to drive IS from northern Syria by carrying out air strikes to support selected rebel groups.