Washington: 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 that "there is still time to do so."
With a November 24 deadline looming for a comprehensive agreement, US Secretary of State John Kerry and Iran`s Foreign Minister Mohammad Javad Zarif met Sunday and again on Monday in Muscat to try to narrow the differences.
US President Barack Obama said Sunday that a "big gap" remains on how the West can have "verifiable, lock-tight assurances" that Iran cannot obtain a nuclear weapon.
"We may not be able to get there," Obama told CBS television`s "Face the Nation."
Obama said US, UN and European sanctions against Tehran would be "slowly reduced" if Tehran meets its obligations under an agreement with the P5+1 -- Britain, China, France, Germany, Russia and the United States.
Iran denies it is seeking a bomb and says its nuclear program aims to produce atomic energy to reduce the country`s reliance on fossil fuels, requiring a massive increase in its ability to enrich uranium in the coming years.
After Kerry and Zarif`s talks, the political directors of the P5+1 powers were due to hold talks in Muscat on Tuesday.
The talks move back to Vienna on November 18 for a final push toward the deadline six days later.