Iran and West end round of nuclear talks, outcome unclear MUSCAT (Reuters) - Iran, the United States and the European Union ended two days of high-level talks on Tehran's nuclear program on Monday with no immediate sign they had bridged gaps ahead of a Nov. 24 deadline for an agreement. A senior Iranian official told Reuters that minimal progress was made in the talks in Oman. "After hours of talks, we could make little progress," the official said. Still differences remain and still we have gaps over issues. In Washington, State Department spokeswoman Jen Psaki said the talks among Iranian Foreign Minister Mohammad Javad Zarif, U.S. Secretary of State John Kerry and EU envoy Catherine Ashton had been "tough, direct and serious." She gave no further details, but said that they were "continuing to chip away at a very challenging issue." Kerry was leaving Oman late on Monday for an Asia-Pacific meeting in Beijing. Diplomats from Iran and the "P5+1" countries - the five U.N. Security Council members, plus Germany - were due to resume talks in Muscat on Tuesday ahead of a last-ditch push in Vienna next week to meet the Nov. 24 deadline. The discussions aim to yield an accord that would put verifiable limits on Iran's uranium enrichment work - and any other potential path to a nuclear weapon - in return for a gradual lifting of sanctions. As they had begun an evening session of the closed-door talks at a luxury hotel, Kerry and Zarif were cautious. Asked whether the negotiating teams were making progress, Kerry merely replied: "We are working hard. We are working hard. Said Zarif: "We will eventually." U.S. President Barack Obama said in a CBS television interview there was still a big gap between Iran and Western powers and said a deal could be out of reach. Economic sanctions led by the United States have pushed Iran to the table for a deal on its nuclear program, Obama said. A final step would involve Iran providing "verifiable, lock- tight assurances that they can't develop a nuclear weapon," he said. There's still a big gap. We may not be able to get there. Western countries suspect Iran has secretly attempted to acquire the means to build nuclear weapons. Iran says it wants peaceful nuclear energy only, but has refused to curb enrichment capacity and has been hit by damaging U.S., EU and U.N. Security Council sanctions. The toughest outstanding issues are the size of Iran's enrichment program, the length of any final accord and the pace at which sanctions would be phased out, diplomats say. Additional reporting by Parisa Hafezi and Fatma Al-Arimi, Editing by William Maclean, Dominic Evans and Bernard Orr