President Barack Obama has signed the New START strategic arms reduction treaty with Russia. The treaty is to take effect by the end of the week.
President Obama's signature is the next-to-last step in the process of putting the treaty into force.
The agreement is expected to be final on Saturday, when U.S. Secretary of State Hillary Clinton and Russian Foreign Minister Sergei Lavrov formally exchange documents at the Munich Security Conference.
The New START treaty will lower the limit on U.S. and Russian strategic warheads from 2,200 to 1,550 during 10 years.
Shortly after the U.S. Senate ratified the agreement last December, Mr. Obama said New START will also reinstate inspections of both countries' strategic weapons.
"This is the most significant arms control agreement in nearly two decades, and it will make us safer and reduce our nuclear arsenals along with Russia's," said Obama. "With this treaty, our inspectors will also be back on the ground at Russian nuclear bases, so we will be able to trust, but verify."
U.S. defense officials say neither country has conducted any inspections since the 1991 START treaty expired in December, 2009. Both nations will be allowed to hold short-notice inspections of each other's nuclear facilities within 60 days of the accord taking effect.
In addition to shrinking both countries' nuclear arsenals, President Obama said in December passage of the treaty would strengthen the important bond between the United States and Russia.
"We will continue to advance our relationship with Russia, which is essential to making progress on a host of challenges, from enforcing strong sanctions on Iran to preventing nuclear weapons from falling into the hands of terrorists," added Obama. "And this treaty will enhance our leadership to stop the spread of nuclear weapons and seek the peace of a world without them."
Mr. Obama and Russian President Dmitry Medvedev originally signed New START last April in Prague. The U.S. Senate approved it on December 22, and the upper house of the Russian parliament, the Federation Council, ratified it on January 26.
The final signing took place in the Oval Office with no reporters present.