MOSCOW — President Barack Obama signed an agreement on Monday to cut American and Russian strategic nuclear arsenals by about a third, a first step in a broader effort intended to reduce the threat of such weapons drastically and to prevent their further spread to unstable regions.
Obama, on his first visit to Russia since taking office, and President Dmitry Medvedev agreed on the basic terms of a treaty to reduce the number of warheads and missiles to the lowest levels since the early years of the Cold War. The new treaty, to be finished by December, would then lead to talks next year on more substantial reductions.
The progress reflected an effort to re-establish ties a year after Russia's war with Georgia left the relationship more strained than any time since the fall of the Soviet Union. The two sides agreed to resume military contacts suspended after the Georgia war and sealed a deal allowing the United States to send thousands of flights of troops and weapons to Afghanistan through Russian airspace each year.
They remained at loggerheads over U.S. plans to build a missile defense system in Eastern Europe, which Washington describes as a hedge against an Iranian nuclear breakthrough and which Russia opposes as a threat in its back yard.
But after hours of meetings at the Kremlin, the presidents agreed to conduct a joint assessment of any Iranian threat and presented a united front against the spread of nuclear weapons.
Obama hailed the arms agreement as an example for the world as he pursued a broader agenda aimed at countering — and eventually eliminating — the spread of nuclear weapons, a goal he hopes to make a defining legacy of his presidency.
While the United States and Russia together have 95 percent of the world's nuclear weapons, Obama also views Russia as an influential player in deterring nuclear programs in Iran and North Korea.
"This is an urgent issue, and one in which the United States and Russia have to take leadership," Obama said. "It is very difficult for us to exert that leadership unless we are showing ourselves willing to deal with our own nuclear stockpiles in a more rational way."
Medvedev expressed willingness to help fight the proliferation of nuclear weapons in places like Iran and North Korea. "It's our common, joint responsibility, and we should do our utmost to prevent any negative trends there, and we are ready to do that," Medvedev said.
Obama and Medvedev used the start of Obama's two-day visit to forge a stronger personal connection. As they waited for a news conference to start in a grand, gold-lined Kremlin hall, Obama and Medvedev whispered and smiled. Speaking with reporters, they professed warm respect for each other. Afterward, they retreated to Medvedev's country estate for dinner with their wives.
Obama will have breakfast today with Prime Minister Vladimir Putin, generally considered the paramount political force in Russia.
The nuclear agreement set the outline for a replacement for the Strategic Arms Reduction Treaty, or START, which expires in December. Once a new treaty is enacted, Obama wants to open talks to cut arms more deeply.
Under Monday's agreement, the START successor treaty would reduce the ceiling on strategic warheads to somewhere between 1,500 and 1,675 warheads within seven years, down from the current ceiling of 2,200 warheads by 2012.
The limit on delivery vehicles — land-based intercontinental missiles, submarines and bombers — would be somewhere from 500 to 1,100, down from the 1,600 currently allowed.