In recent years, Russia has become more dependent on its nuclear weapons. For instance, it has been committed to developing new strategic delivery vehicles, along with new strategic nuclear submarines. Meanwhile, it has linked the reduction of strategic weapons with a scaling back of U.S. missile defense initiatives to ensure that any re-deployment of U.S. missile defense systems will not exceed the current level.

But the United States has held that the new treaty should primarily concern strategic offensive weapons, and that the issue of missile defense should be discussed separately.

In fact, Obama faces serious challenges at home when it comes to altering missile defense deployments. Neither the Congress nor the Pentagon would accept any substantial limitation with the missile defense program.

Bones of contention

Although these differences could be regarded as being grounded in technical problems, the delay in the evolution of the new treaty demonstrated the climate of relations between the United States and Russia. It also revealed their divergent perceptions of nuclear weapons.

The two countries have long agreed in principle to reductions in nuclear arms, which are not only practical in terms of security, but also fiscally. Nevertheless, difficulties still haunted their negotiations—including how to keep a strategic balance between the two countries, and how to maintain the effectiveness of their nuclear deterrence.

The United States insisted that the new treaty should ensure a reduction in the event that Moscow did not live up to its promises. Persuading Russia to join the nuclear disarmament process is the main driving force for the United States' push toward a new strategic arms treaty.

On the contrary, Russia emphasized the balance of strategic power during the negotiations. It is of the view that while conducting nuclear disarmament, factors such as outer space weaponization, missile defense and conventional forces should also be taken into account.

This demonstrated that, to a great extent, Russia's distrust of the United States has never fully decreased. That's why it bargained with the United States in nuclear disarmament talks in a bid to maintain its nuclear deterrence as much as possible.

When Russia penned the START treaty with the United States in 1991, the Soviet Union was on the brink of disintegration. Weak as it was, it made significant concessions to the United States.

But in the end, most of the promises the Untied States made were not kept. Soon after its political transformation, Russia embarked on a change in its foreign policies. Over the past 19 years, Russia's strength has improved markedly. As a result, it has been able to negotiate with the United States on an equal footing.

Moreover, nuclear weapons are now one of the major pillars supporting Russia's national security—a sharp contrast with the Cold War era when NATO allies resisted the Soviet Union's conventional weapons prowess with their own nuclear capabilities.

Although presidents Obama and Medvedev have both declared their shared goal of a nuclear-free world, the two still hold different views on many issues. President Obama's concept of a nuclear-free world is attractive, but it is far from being universally accepted.

Russia does not completely believe in Obama's proposal and feels that the 44th U.S. president has ulterior motives. Without a vigorous response by Moscow, U.S. efforts will be, at best, a waste of time.

In this sense, the reasons behind the delay of the new treaty lay beyond the realm of technical problems, and had instead morphed into a highly charged point of contention between the two powers.

Even after the new treaty is signed, the legislative approval process will likely take some time. In 1991, it took more than 400 days for the U.S. Congress to approve START from the day it was signed.

It seems that the process may not take so long this time around. But Obama's markedly decreased influence within Congress since assuming office portends to lengthen ratification.

The author is director of the Center for Arms Control and International Security at the China Institute of International Studies and now a visiting scholar at Stanford University's Center for International Security and Cooperation