The top U.N.disarmament official expressed optimism Tuesday that the United States and Russia could reach a new deal on reducing nuclear weapons after the two sides resumed talks in Geneva. Sergio Duarte, the U.N. high representative for disarmament affairs, said he was confident the two countries would negotiate an agreement to succeed a 1991 accord that has expired. “I think that's very important that they continue the track and they arrive at the results,” Duarte said on the sidelines of a nuclear disarmament workshop in Manila, the Associated Press reported. The two sides resumed long-running talks about a successor to the 1991 Strategic Arms Reduction Treaty (START) on Monday. The negotiations were supposed to be finished before the treaty-which limited the number of nuclear warheads and carrier systems each side could deploy-expired on December 5. “I expect that they will reach an agreement, a follow-on to the START, and I hope that they also point the way to future agreements,” Duarte said. Duarte was in Manila for a two-day workshop of global disarmament experts to prepare for a conference at the United Nations in May to review the nuclear Non-Proliferation Treaty. The Philippines has been elected to head the review of the treaty, which entered into force in 1970 and is reviewed every five years.