The United States said Monday that talks underway in Oman between world powers and Iran on its nuclear program have proved "tough, direct and serious."

The United States said Monday that talks underway in Oman between world powers and Iran on its nuclear program have proved "tough, direct and serious."

State Department spokeswoman Jen Psaki said in Washington that the United States remains "very focused on making progress" and insisted "there is still time to do so."

The United States, Iran and the European Union held a second day of talks in the Omani capital, Muscat aimed at breaking the deadlock on a nuclear deal Monday, with the clock ticking down to a November 24 deadline.

Iranian Foreign Minister Mohammad Javad Zarif, his US counterpart John Kerry and chief European Union (EU) envoy Catherine Ashton kicked off fresh trilateral discussions in Muscat on Monday over outstanding issues regarding Tehran’s peaceful nuclear energy program. They resumed their negotiations just before 11:30 am (0730 GMT), a US official said, but the meeting was closed to the press.

On Sunday, the three senior officials held two rounds of intensive negotiations aimed at facilitating the conclusion of a permanent nuclear agreement between Iran and the six countries – Russia, China, Britain, France, the US and Germany.