US Ambassador to Israel Dan Shapiro on Wednesday said "Iran's window of opportunity is rapidly closing."
"We will do everything we can to achieve a diplomatic solution but we do not intend to continue talks for talks," Shapiro said during a Security Studies conference in Tel Aviv.
He added that the US will be taking steps "to increase pressure" on Iran to ensure it does not obtain nuclear weapons.
His remarks come after a second round of talks between Iran and the P5+1 – the five permanent members of the UN Security Council plus Germany – failed again to yield results as the West pressures Tehran to halt its controversial uranium enrichment program.
Shapiro made a similar comment before the Baghdad talks. His remarks on Wednesday, however, may indicate a growing sense of urgency.
A third round of talks has been scheduled for Moscow, but there is mounting pessimism about whether Iran is participating in good faith.
“I see no evidence whatsoever that Iran is ready to end its nuclear program,” Prime Minister Binyamin Netanyahu said shortly before last week's talks in Bagdad.
Defense Minister Ehud Barak also told reporters he was "skeptical" that Iran was serious and charged Tehran was using the talks to buy time for nuclear weapons research.
As a signatory to the Nuclear Non-Proliferation Treaty, Iran is forbidden from pursuing nuclear weapons related research and must give IAEA inspectors full access to its nuclear facilities.
Two IAEA reports in recent months have cited credible intelligence sources indicating Iran is conducting nuclear weapons research, and noted Iran's systemic obstruction of inspection efforts.
IAEA chief Yukiya Amano in March went on record saying "Iran is not telling us everything."
His remarks came after Iran denied inspectors access to the Parchin military facility, where IAEA experts believe high-explosives research for nuclear detonation is taking place.
Meanwhile, recent satellite photos of the military site in Iran indicate the Parchin site is being cleared, raising suspicion that Iran is attempting to hide incriminating evidence.
According to two anonymous participants in a closed briefing for diplomats of the International Atomic Energy Agency, there were also photographs.
According to the sources, one of the buildings that appeared in previous satellite photographs – believed to have been a specialized explosives test chamber – has now "disappeared from the site."