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U.S. President Barack Obama and Russian President Dmitry Medvedev shake hands after signing the new Strategic Arms Reduction Treaty (START II) at Prague Castle in Prague, April 8, 2010. [Photo/Agencies] |
Steven Pifer, an arms control expert at the Brookings Institution, said the pact with Russia would give the US delegation more credibility at the non-proliferation conference.
"If the United States and Russia were to show up with no agreement and between the two of them controlling 95 percent of the weapons, it's pretty easy for the non-nuclear states to say, 'well you're not doing your part, why should we?'," Pifer said.
Obama's new nuclear strategy document broke with former President George W. Bush's threat of nuclear retaliation in the event of a biological or chemical attack.
The assurance applies only to countries in compliance with the nuclear Non-Proliferation Treaty, so Iran and North Korea would not receive that commitment.
On Tuesday, Russian Foreign Minister Sergei Lavrov repeated Moscow's threat to withdraw from the START II treaty if US plans for missile defence threatened Russia.
Obama has put a priority on trying to "reset" relations with Moscow that hit a post-Cold War low during Russia's 2008 war with Georgia, and the treaty could help that.
The successor to the 1991 Strategic Arms Reduction Treaty would limit operationally deployed nuclear warheads to 1,550, down nearly two-thirds from START I. However, it does not limit shorter-range tactical nuclear weapons.