U.S. President Barack Obama plans to meet with his Russian counterpart Dmitri Medvedev, in Moscow in early July. (July 6-8). One of the issues to be discussed is a new pact to replace the Strategic Arms Reduction Treaty that expires this December.

During a meeting in London April 1, President Barack Obama and his Russian counterpart, Dmitri Medvedev, agreed to resume talks to replace the START-One treaty.

A few days later (April 5) during a speech in Prague, Mr. Obama sounded confident.

"To reduce our warheads and stockpiles, we will negotiate a new strategic arms reduction treaty with the Russians this year. President [Dmitri] Medvedev and I began this process in London, and will seek a new agreement by the end of this year that is legally binding and sufficiently bold," he said then.

The START-One treaty was negotiated in the 1980s, signed in 1991 by U.S. President George Herbert Walker Bush and Soviet President Mikhail Gorbachev.  It came into force in 1994.

More than 1,000 pages long, the START agreement is one of the most complex treaties in history dealing with reducing nuclear weapons.

Daryll Kimball, Executive Director of the Arms Control Association, a private, independent organization, says START-One was a landmark treaty.

"It came just as the Soviet Union was breaking up, as the Cold War was ending. It slashed U.S. and Russian strategic nuclear stockpiles from about 10,000 warheads each down to 6,000 by the year 2001," he said.  "It also limits the number of strategic delivery systems - the missiles and the bombers that carry those nuclear weapons - to no more than 1,600 on each side. And it also established a far-reaching monitoring and verification system, including 12 kinds of on-site inspections and important data exchanges about each country's respective missile stockpiles and their flight characteristics," said Kimball.

Following their April 1 meeting, presidents Obama and Medvedev issued a statement saying the two sides will work on a legally binding document and try to reach levels lower than those contained in another agreement - the 2002 Moscow Treaty. That agreement committed both sides to cutting arsenals to between 1,700 and 2,200 warheads by 2012. The two presidents instructed their negotiators to present a progress report during the July Moscow summit.

Kimball says it is crucial to achieve deep reductions in long-range nuclear arsenals.

"The United States deploys about 2,200 strategic warheads - the Russians somewhere between 2,000 and 3,000. Many of these weapons are on a high state of alert, they can be launched within minutes and it simply is a posture, a nuclear posture that's out of step with current day realities," he said.

David Kramer, a former senior U.S. State Department official in the Bush administration, (now with the German Marshall Fund in the United States) says despite both sides' commitment to reducing strategic nuclear weapons, there are differences to be resolved.

"The differences on START have to do with what one does with warheads once they are removed - and the storage of missiles. There is no debate any more about the treaty being legally binding - there's agreement on that. But it's a question of counting, and what qualifies as a warhead, and what one does with them after: whether they should be destroyed or held in storage somewhere," he said.  "There is some discussion back and forth about the numbers. It is an issue about how low the two sides can go. Under the Moscow Treaty, the two sides could go as low as 1,700. The talk now in this post-START agreement is for something around 1,500 - some have been pushing for a lower number," said Kramer.

Analysts also say it will be interesting to see whether Moscow will link any progress in the post-START talks to the U.S. abandoning its plans for a missile defense shield in Eastern Europe. U.S. officials have rejected any linkage.

David Kramer says in the final analysis, Moscow needs the treaty more than Washington does.

"Because their nuclear weapons infrastructure is deteriorating and they aren't able to maintain their current levels - number one. Number two, if - and no one is advocating this - if somehow there were a renewed arms race, Russia couldn't compete. And so Russia has every interest in lowering the levels between the two sides," he said.

Analysts say Russian and American negotiators are facing a tight timeline. They say while the START-One treaty expires December 5,  a new agreement must be reached by August in order for the ratification process to go through the U.S. Senate and the Russian parliament before the treaty's demise.