RIYADH: 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, warning that Iran's window for a peaceful resolution will "not remain open for ever."

"Our policy is one of prevention, not containment," Clinton told a news conference in the Saudi capital after talks with her Gulf Arab counterparts, confirming that the venue would be Istanbul as preferred by Iran.

Iranian Foreign Minister Ali Akbar Salehi announced the date last Wednesday.

He said at the time that Iran considered Istanbul -- the location of the previous round of talks, which collapsed in January 2011 -- the "best place" but that options were still being discussed.

"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," Clinton said.

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.

"It soon will be clear whether Iran's leaders are prepared to have a serious, credible discussion about their nuclear programme, whether they are ready to start building the basis of a resolution to this very serious problem," she said.

"It's up to Iran's leaders to make the right choice.

"We will see whether they will intend to do so starting with the P5 plus-1 negotiations in Istanbul April 13 and 14," she said.

"What is certain, however, is that Iran's window to seek and obtain a peaceful resolution will not remain open for ever."

Clinton later travelled to Istanbul for a conference on Syria and was due to meet Turkish Prime Minister Recep Tayyip Erdogan, who recently returned from a visit to Tehran focusing on Iran's nuclear programme and bilateral ties.

It was likely the two would discuss the Iranian nuclear issue.