Kerry: Big, serious gaps remain in Iran nuclear talks. Possible impasse hinted at. VIENNA - Negotiators working to slow Iran's nuclear program and ease sanctions on the country resumed talks Saturday and dropped hints that they were at an impasse with just two days left before a deadline for an accord. In brief remarks before going into a closed-door meeting, Secretary of State John F. Kerry characterized the talks with Iran as "difficult" and marked by "serious gaps. His German counterpart, Frank-Walter Steinmeier described the remaining time before Monday's deadline as "the hours of truth." Before reporters were escorted out of the room, Kerry was overheard making small talk with Steinmeier, saying "We're stuck," and "We were ready to go." On Friday, both Kerry and Iranian Foreign Minister Mohammad Javad Zarif announced plans to leave Vienna for consultations, but they both ended up reversing themselves and holding a two-hour meeting, instead. Zarif told the Iranian media that he did not consider the plan put forth by the United States and the five other nations that are its negotiating partners strong enough to run past Tehran. Kerry acknowledged Saturday that the talks with Iran were a tough slog. "We're working hard," he told reporters before meeting with Steinmeier, "and we hope we're making careful progress. But we have big gaps, we still have some serious gaps, which we're working to close. Steinmeier, speaking in English made reference to the ticking clock for Monday's deadline, when an interim agreement reached a year ago freezing Iran's nuclear program expires, unless they extend it. "This is the weekend, or these are the hours of truth," Steinmeier said. We have to check now if Iran is really ready to move in the right direction. The only criterion for a deal about the nuclear issue . . . is the main question: If Iran is really ready to renounce every research development working in the direction of getting nuclear weapons. Kerry is scheduled to meet Saturday afternoon with Zarif and the European Union representative, Catherine Ashton. He spent the morning working the phones, speaking with foreign ministers from Turkey, Kuwait, Qatar, Bahrain and the United Arab Emirates, and meeting with French Foreign Minister Laurent Fabius. In Iran, there were signs that the approach taken by the negotiators is meeting some important approval. The Iranian armed forces chief of staff, Hassan Firouzabadi, praised the performance of the Iranian team in an interview posted Saturday by the Iranian news agency IRNA. Firouzabadi described the talks as an opportunity, and said that the American position in talks earlier this month in Oman was "what the Zionist regime wanted them to say." With two days remaining before an interim agreement expires, negotiations are bedeviled by what the Iranians will concede and the demands of the six other nations conducting the talks. The issues have narrowed to several key points: the extent of Iran's ability to make nuclear fuel, the level of U.N. monitoring, and how much Iran can expect to have international and U.S. economic sanctions eased in exchange for concessions.