WASHINGTON — US Secretary of State John Kerry will head to the Gulf next month to allay fears over the Iranian nuclear deal. The announcement came after Kerry held talks in Washington with Saudi Foreign Minister Adel Al-Jubeir, who used the occasion to warn Iran against any further “adventures” in the region. “If Iran should try to cause mischief in the region, we're committed to confront it resolutely,” said Jubeir. Al-Jubeir added that all Mideast countries want to see a peaceful solution to the Iranian nuclear program. “They have welcomed the agreement that is based on a strong and continuous inspection system to reassure Iran's adherence to all the accord's clauses,” he said. Al-Jubier stressed that there should be an effective and prompt mechanism to allow quick reimposition of sanctions in case Tehran violates the agreement. Al-Jubeir's warning came as Washington and London sought to ease concerns over the nuclear accord, even as Iran's supreme leader warned major powers are not to be trusted over its implementation. As part of an international charm offensive, British Foreign Secretary Philip Hammond met Israeli Prime Minister Benjamin Netanyahu, who strongly opposes the landmark accord. Netanyahu has condemned the deal with Israel's arch-foe as a “historic mistake” and hinted at a possible military response. US Defense Secretary Ashton Carter is also due in Israel next week and Israeli opposition leader Isaac Herzog is to visit Washington, partly to push for security guarantees. The UN Security Council is now expected to endorse the deal on Monday, diplomats said. The resolution is expected to pass without difficulty as its five veto-wielding permanent members — Britain, China, France, Russia and the United States — negotiated the accord, along with Germany. In a boost to the agreement, more than 100 former US ambassadors, including the ranking diplomat taken hostage in Tehran in 1979 when students stormed the American embassy, praised it as a “landmark”. “If properly implemented,” they said in an open letter, it “can be an effective instrument in arresting Iran's nuclear program”. But in Iran, supreme leader Ayatollah Ali Khamenei warned President Hassan Rohani that “some” world powers are not to be trusted in implementing it. In a letter to Rohani, Khamenei, who had the final word on the agreement, congratulated Iran's negotiators for “their tireless efforts”. Bringing the talks to a close was a “milestone”, Khamenei said, but the agreement requires “careful scrutiny” before it is approved. — Agencies