Paris – Nearly a year after President Barack Obama and Russian President Dmitry Medvedev ordered negotiators to start work on a new treaty to reduce their nuclear arsenals, the two countries say they are finally close to completing a deal — taking a small but important step toward the U.S. leader's goal of a nuclear-free world.

A deal could build momentum and trust toward resolving other key nuclear issues. They range from how to pressure Iran and North Korea to abandon their nuclear ambitions to reducing the number of tactical nuclear weapons that are so unpopular in Europe. It could also set a positive tone for a key conference on nuclear non-proliferation this spring.

On another level, it could bolster Obama's credibility, which is being battered on multiple fronts: the disappointing results of the Copenhagen climate change conference, ongoing economic miseries, faltering Middle East peace efforts and growing skepticism about last year's Prague speech in which he promised to rid the world of nuclear weapons.

"It's important to show the Prague speech was not just rhetoric," Mark Fitzpatrick, senior fellow for non-proliferation at the London-based International Institute for Strategic Studies, told The Associated Press.

An agreement would end a drought in disarmament accords between the United States and Russia, which were a hallmark of the Cold War years and were negotiated even during the worst periods of tension between them. It officially would reconfirm Moscow's nuclear superpower status, which remains an essential element of its national identity and prestige.

"For Russia, it's the mother of all the negotiations," said Thomas Gomart, head of the Russia Center at the French Institute for International Relations in Paris, said in an interview. The magnitude of Russia's nuclear arsenal, Gomart says, is what distinguishes it from other nuclear powers and is the "ultimate guarantee" of superpower rank.

The negotiations under way in Geneva are intended to replace the 1991 Strategic Arms Reduction Treaty, which expired in December, and are likely to limit the number of deployed strategic warheads by the United States and Russia. Any agreement would need to be ratified by the legislatures of both countries and would still leave each of them with a large number of nuclear weapons, both deployed and stockpiled.

Both U.S. Secretary of State Hillary Clinton and Russian Foreign Minister Sergey Lavrov said following talks in Moscow last week that a deal was near — but not done.

Officials and analysts differ on just how close the two sides are and just what issues are still keeping them apart. An official with knowledge of the talks who spoke on condition of anonymity because he was not authorized to speak publicly said Friday that the "focus is on technical issues and not on posturing."

Even as negotiations continue, a series of other important meetings on nuclear security  loom. Obama will host a nuclear security summit of some 40 nations on April 12-13 in Washington.

A review conference on the 40-year-old Nuclear Nonproliferation Treaty will be held at the United Nations in May.

Successful completion of a START replacement treaty could have an impact on those summits, as well as on Obama's efforts to get the U.S. Senate to ratify the Comprehensive Test Ban Treaty, efforts to make progress on the Fissile Material Cutoff Treaty and a Russian initiative to establish an international nuclear fuel enrichment center in Siberia.