Russian plan to negotiate deeper cuts in nuclear weapons fits well with each country's shifting focus: the United States toward more reliance on precision conventional weapons, and Russia toward more modern short-range nuclear weapons to offset US conventional superiority. The “joint understanding” hailed Monday by President Barack Obama and Russian President Dmitry Medvedev would direct negotiations to set substantially lower levels of nuclear warheads for both countries. The United States, which once counted on an enormous arsenal of nuclear bombs and missiles to offset the conventional arms predominance of its Cold War rival, now bases its security more on modern non-nuclear weaponry like the precision-guided bombs and missiles it used in toppling governments in Iraq and Afghanistan. While the United States has dismantled parts of its nuclear stockpile in recent years, Russia has taken a different, cheaper approach. It is investing more in its nuclear force, including parts that are not limited by any treaty. Meanwhile, Moscow has been shrinking much of its creaky, underresourced conventional force. That helps explain why the Russians favor lower warhead limits so long as they are still able to modernize the remaining nuclear force. Russia also wants the reductions to be tied to cuts in the allowable number of “delivery vehicles,” the missiles and bombers that deliver nuclear warheads to their targets. Motivating the Russians is that they already have far fewer long-range missiles and bombers than do the Americans, about 800 at last count, compared to about 1,200 in the US military. In their Moscow talks Monday, Obama and Medvedev agreed that their negotiators would work out a new limit on delivery vehicles of between 500 and 1,100. The low end of that range favors the Russians, since they already are well below the 1,100 figure. They also agreed that warhead limits would be reduced from the current range of 1,700-2,200 to as low as 1,500. The United States now as about 2,200 such warheads, compared to about 2,800 for the Russians. These are so-called strategic warheads, meaning for use on long-range attack missions. Tactical nuclear warheads, for battlefield use, will not be counted in the proposed new treaty. Russia has far more tactical warheads than does the United States, which got rid of most of its tactical weapons in the early 1990s. The fact that Obama and Medvedev agreed to launch negotiations on a new treaty marks a big change from just a few years ago. The administration of President George W. Bush had long refused the idea of new legally binding limits on strategic nuclear weapons, although it changed its tune in late 2007. Bush's view was that arms control treaties were a relic of the Cold War, not relevant to contemporary US security interests. Obama and Medvedev take a different view, having embraced the goal of eventually eliminating all nuclear weapons. For the Russians, the move fits in with their long-term stated goal of a nuclear-free world. It also is about the practical reality of having a Soviet-era fleet of land-based missiles, missile-toting submarines and long-range bombers that is decrepit compared to a more modern US arsenal. “So the Russians have to make some investment decisions,” said Steven Pifer, a career diplomat who specializes in Russia issues at the Brookings Institution think tank. “If they can reduce forces levels on both sides, it means less money that they'll have to put into new strategic arms.” In their remarks Monday, Obama and Medvedev both underscored the urgency of concluding a new treaty. That is because an existing one – known as START 1 and containing the only legally binding rules for verifying and monitoring US and Russian nuclear weapons levels – is due to expire Dec. 5.