The US secretary of state renewed her call to Iran to start serious talks on its nuclear program, stressing that a window for negotiations will not be open indefinitely

The US secretary of state renewed her call to Iran to start serious talks on its nuclear program, stressing that a window for negotiations will not be open indefinitely.

"Our message to Iran is clear: our window remains open to resolve the international community's concerns about your nuclear program diplomatically ... but that window cannot remain open indefinitely," Hillary Clinton told reporters Tuesday in Sarajevo, the first leg of her five-nation Balkans tour.

Clinton voiced hope that Tehran would soon start "serious, good faith negotiations" over the issue.

The last round of direct talks in Moscow in June included mentions of a new meeting possibly being held in a neutral venue such as the Kazakh capital Astana or Beijing.

Meanwhile, Iran and the United States have recently both denied any deal had been reached for one-on-one nuclear talks, as The New York Times reported—even though the White House said it was open to such dialogue.