By Sebastian Sprenger / April 8, 2010 at 5:00 AM

President Obama and Russian President Dmitry Medvedev signed the "New START" pact in Prague today, laying the groundwork for the extension of a nuclear disarmament agreement that has been key to relations between the two countries for decades. To enter into force, both countries' parliaments must ratify the treaty.

"While the New START treaty is an important first step forward, it is just one step on a longer journey," Obama said in a statement posted on the White House Web site today. "As I said last year in Prague, this treaty will set the stage for further cuts. And going forward, we hope to pursue discussions with Russia on reducing both our strategic and tactical weapons, including non-deployed weapons," the statement reads.

The nuclear arsenals of Russia and the United States make up more than 90 percent of the world's atomic weapons.

The treaty text enables Washington and Moscow to continue their work on ballistic missile defense shields, an ongoing point of contention regarding a planned U.S. system for Europe. "A missile of a type developed and tested solely to intercept and counter objects not located on the surface of the Earth shall not be considered to be a ballistic missile to which the provisions of this Treaty apply," the treaty states.

"President Medvedev and I have also agreed to expand our discussions on missile defense," Obama's statement reads. "This will include regular exchanges of information about our threat assessments, as well as the completion of a joint assessment of emerging ballistic missiles. And as these assessments are completed, I look forward to launching a serious dialogue about Russian-American cooperation on missile defense," the statement adds.