Riyadhi, Saudi Arabia ? U.S. Secretary of State Hillary Rodham Clinton made clear Saturday that time is running out for diplomacy over Iran’s nuclear program and said talks aimed at preventing Tehran from acquiring a nuclear weapon would resume in mid-April.

With speculation over a possible U.S. or Israel military attack adding urgency to the next round of discussions in Istanbul set for April 13, Clinton said Iran’s “window of opportunity” for a peaceful resolution “will not remain open forever.”

She also expressed doubt about whether Iran has any intention of negotiating a solution that satisfies the U.S., Israel and other countries that believe Iran is trying to develop nuclear weapons. Tehran contends the program is solely for peaceful energy and research purposes.

“We’re going in with one intention: to resolve the international community’s concerns about Iran’s nuclear program,” Clinton told reporters after attending a security conference in Saudi Arabia.

“Our policy is one of prevention, not containment. We are determined to prevent Iran from obtaining a nuclear weapon,” America’s top diplomat said.

“We enter into these talks with a sober perspective about Iran’s intentions. It is incumbent upon Iran to demonstrate by its actions that it is a willing partner and to participate in these negotiations with an effort to obtain concrete results.”

Her remarks followed President Barack Obama’s announcement Friday that the U.S. was moving ahead with penalties aimed at depriving Iran of oil revenue, while also working with Saudi Arabia and other Persian Gulf states to ensure ample global petroleum supplies.

Clinton prodded Gulf governments to develop a coordinated defense strategy against Iranian missiles. With tensions rising in the region, she said American and Gulf militaries should cooperate to improve maritime security as well.

Underscoring the limits of U.S.-Gulf cooperation, however, U.S. officials confirmed Saturday that the United Arab Emirates had shut down an American-funded democracy group, following similar Emirates action against a German organization this past week.