Updated

CIA Director John Brennan, ‎in an interview with "Fox New Sunday," claimed the U.S. and other negotiators are better-positioned than they were in the past to verify Iran's end of any potential nuclear deal, as talks near a key deadline.

"I think we've gone to school on some of those developments over the last decade or so, so that we can now have a better plan and an opportunity to verify some of the things that they are saying that they're going to do and not do," he said.

Secretary of State John Kerry, meanwhile, said "important gaps remain," but he also said there has been progress.

Kerry and Iran President Hassan Rouhani spoke at the conclusion of a week of talks in Switzerland. They will return for at least one more meeting before the preliminary deadline.

Kerry also said he will stop in London later Saturday before returning to Washington to talk with France and United Kingdom leaders involved in the negotiations to “share ideas this evening on how to resolve remaining sticking points … to determine whether a deal is possible.” He also said he has already spoken with China and Russia.

Sunday Show exclusive with CIA Director John Brennan this week on Fox News Sunday March 22 – 2P/6P ET Fox News Channel & check local listings.