US Secretary of State John Kerry said on Monday that talks with Iran about its nuclear program are time-limited.
"We both prefer - and this is important for Iranians to hear and understand - we both prefer diplomacy as the first choice, the preferred choice," Kerry said, speaking at a news conference at the Al-Yamamah Palace in Riyadh.
"But the window for a diplomatic solution simply cannot by definition remain open indefinitely," Kerry added.
Western powers suspect Iran of covertly developing nuclear weapons technology, while Tehran claims its program is exclusively for energy and research-related purposes.
Kerry, who spoke in Saudi Arabia, is making the diplomatic rounds in his first overseas trip as secretary of state. He will visit next the United Arab Emirates, Qatar and then return to the US on Wednesday, the Associated Press reported.
Kerry's remarks follow a request by UN nuclear watchdog chief Yukiya Amano for access to an Iranian military site.
"I request Iran once again to provide access to the Parchin site without further delay," Amano said, according to Reuters, which quoted a copy of his speech from a private meeting.
So far the International Atomic Energy agency has been, as Amano said, "unable to report any progress on the clarification of outstanding issues, including those relating to the possible military dimensions to Iran's nuclear program."
Talks between Iran and six world powers - the US, China, France, Russia, Britain and Germany - concluded in Almaty, Kazakhstan on Feb. 27. Negotiations are supposed to resume on April 5, according to Bloomberg News.