The Gulf states generally welcomed the deal, and Iran's foreign minister this week paid visits to four of them Kuwait, Oman, Qatar and the United Arab Emirates in an early indication of the warming ties.
Even so, Gulf leaders remain suspicious of Iran's broader intentions and fear that better relations with the West could embolden Tehran, destabilizing the region. Heavyweight Saudi Arabia in particular sees Iran as a threat to its own influence, and it and other Sunni-ruled Gulf nations are important backers of the Syrian rebels fighting to topple the Iran-allied government of Bashar Assad in Syria.
The Gulf states also blame Iran for stoking the nearly three-year Shiite uprising in Sunni-ruled Bahrain, a key regional ally of the United States and Britain. The small island kingdom, a former British protectorate, hosts British minesweepers and is home to the U.S. Navy's Fifth Fleet.
Opposition protesters again took to the streets just hours before Hague's speech. The country's majority Shiites have been holding regular demonstrations demanding greater reforms from the Sunni monarchy since 2011, and clashes frequently break out between protesters and the police.
Hague sought to make clear that any progress on improved relations with Iran should not come at the expense of its Arab allies across the Persian Gulf.
"I assure you that the agreement with Iran does not for us in the UK imply diminution of our commitment to our alliances in the region or to the security of its vital sea lanes or to the struggle to end terrorism," he said. "Engagement on the nuclear issue should not mean a free pass for Iran on other issues in the region."
Hague's comments at the Manama Dialogue, hosted by the International Institute for Strategic Studies think tank, echoed those made by U.S. Defense Secretary Chuck Hagel aboard a U.S. Navy ship docked in Bahrain that were aimed at reassuring regional allies.
The defense chief said it remains to be seen whether Tehran is serious about keeping its nuclear development peaceful, and that the U.S. has no plans to change its military posture in the region over the next several months.
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