PRAGUE — President Obama and Russian President Dmitry Medvedev on Thursday signed a new arms-control treaty designed to open a new era of harmony between the former superpower rivals while launching an arms agenda extending far into the future.
The two leaders met in a medieval castle in Prague, once a city at the epicenter of Cold War tension, and formally agreed to bring their nations' arsenals to their lowest levels in half a century.
The treaty marks the most important step yet in Obama's effort to reset relations with Russia, which he said have drifted after their low point of August 2008, when Russia invaded neighboring Georgia.
"Together, we have stopped the drift and proven the benefits of cooperation," Obama said. "When the United States and Russia are not able to work together on big issues, it is not good for either of our nations, nor is it good for the world."
Medvedev said the treaty would "open a new page" in Russian-American relations.
But the signing of the pact also pointed to the challenges Obama confronts as he presses forward with plans to control the world's arms and address future international security threats.
The New START treaty, named for the Strategic Arms Reduction treaties of the 1990s, resulted from eight months of contentious negotiation and represents the first in a series of steps Obama has planned with the goal of scaling back the world's reliance on nuclear arms.
Next week, Obama hosts a meeting of the heads of more than 40 nations in Washington, D.C., to forge an agreement on better safeguarding nuclear materials that could fall into the hands of terrorists. In May, U.S. officials hope to persuade other world powers to strengthen the fraying nuclear Non-Proliferation Treaty, the central agreement on world efforts to halt the spreading of nuclear weapons.
There is also uncertainty about ratification of New START. While White House officials said they expect to line up the 67 Senate votes needed for ratification this year, the Senate is polarized and entering a highly charged midterm election season.