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.
Europe and other nations on the sidelines of the START talks have a vital stake in their outcome too, because deep cuts in nuclear arsenals could slow proliferation, said Alexander Savelyev, a disarmament expert with the Russian Academy of Sciences.
"From the international point of view, this treaty will be extremely important," he said, because it would strengthen the 1970 Nuclear Non-Proliferation Treaty, which called for a gradual disarmament. "This new agreement, I hope, will help prove that the non-proliferation treaty is still active, is still effective and will remain in force."
Having a START replacement signed before the Washington and New York summits could possibly help persuade other countries to cut their arsenals or to refrain from expanding or developing their programs given that the two major nuclear powers are taking steps to reduce theirs.
It could also help the Europeans advance their goal of removing U.S. tactical nuclear weapons from their territory.
Belgium, Germany, Luxembourg, the Netherlands and Norway -- all NATO members -- plan to discuss having the United States eliminate its nuclear arsenal deployed in Europe at the NATO summit in Lisbon in November. The Europeans long have chafed at having these weapons on their territory.
"Hopefully, it will create the momentum to do more," said Fitzpatrick of the International Institute for Strategic Studies. "This agreement will be very important for setting the tone for the NPT review conference," he added.
While a new START treaty would be an important step to show the rest of the world that Russia and the United States are serious about nuclear downsizing, it will in no way result in a nuclear-free world in the short term. Many challenges remain in the way of that goal.
One Kremlin official, who asked not to be identified because he was not authorized to speak on the subject, said Friday that Russia recognizes that pushing for a ban on nuclear weapons could help slow their spread. "We understand the importance of going toward a zero nuclear world," he said.
He said that, as a practical matter, the world will never eradicate nuclear weapons. "It's obviously an unachievable goal," he said, because there would always be rogue states and terrorists who would want to obtain them.
Western experts too say there are obstacles to a nuclear-free world, including Russia itself.
For the Kremlin, nuclear weapons remain an important bargaining chip for other things that Russians want, namely preventing the deployment of a missile defense system and reductions on conventional weapons in Europe. Russia is also wary of China and would never give up all of its weapons as long as the Chinese had theirs.
"They (Russians) won't want to go much lower," Fitzpatrick said.
A START deal, however, would reverse a downward trend in relations between the United States and Russia that reached their nadir under former President George W. Bush and only slowly have begun improving under Obama and the now famous "reset button" in the strategic relationship between Washington and Moscow.
"This will be a manifestation that they will be talking and cooperating again," said Fitzpatrick.
The rest of the world also has a stake in good relations between the two leading nuclear powers, Savalyev said.
"I believe it might be very meaningful, since the level of our relations are not very good," said the disarmament expert with the Russian Academy of Sciences. "I personally hope that it might be a turning point from a cold peace to real cooperation.