The United States wants "concrete results" at talks between Iran and world powers on April 13 in Istanbul on Tehran's nuclear programme, US Secretary of State Hillary Clinton said on Saturday.
"Our policy is one of prevention, not containment," Clinton told a press conference in the Saudi capital after talks with her Gulf Arab counterparts.
"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," said Clinton.
US President Barack Obama has made clear that there is still time for diplomacy to work "provided Iran comes to the talks prepared for serious negotiations," she said.
Israel has brandished the threat of possible military action against Iran's nuclear sites, while the United States has put its energies into sanctions and diplomacy but has not ruled out the military option.
The last round of talks between Iran and the P5+1 comprising the United States, Russia, France, Britain, China and Germany, held in Istanbul last year ended in failure.
The United States and its Western allies believe Iran is working towards a nuclear weapons capability. Tehran denies that, saying its atomic programme is exclusively peaceful.
"I want to underscore... there is not an open-ended opportunity for Iran" over its nuclear programme, said Clinton.