Both countries are required to report key figures from their nuclear weapons arsenals as part of the landmark new Strategic Arms Reduction Treaty (START) adopted by Moscow and Washington on February 5.
The United States has 882 deployed intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs) and heavy bombers, compared with 521 for Russia, according to the State Department, which published the new START aggregate numbers.
The United States also has 1,800 deployed warheads and 1,124 launchers, as well as deployed and non-deployed heavy bombers, compared with Russia's 1,537 deployed warheads and 865 launchers and heavy bombers, according to the figures.
The figures are current as of February 5, 2011, "as drawn from the initial exchange of data by the parties" that was required within 45 days of the treaty coming into force.
The new START limits each side to 1,550 deployed warheads and 700 deployed ICBMs and SLBMs and heavy bombers, meaning the United States would still need to reduce its arsenal under the terms of the treaty.
The first nuclear pact in two decades has been feted as vital to global security because it reduces old warhead ceilings by 30 percent from a limit set in 2002, and establishes a streamlined new inspection procedure designed to eliminate cheating.
In October 2009, two months before the end of the original START treaty, the State Department issued strategic offensive arms figures that showed the United States possessed 5,916 "attributed" warheads, compared to Russia's 3,897.
A person familiar with START described it as a "totally different counting system" than the new START, which uses a more accurate counting in listing 1,800 actually deployed US warheads on ICBMs, SLBMs or heavy bombers.
A more realistic comparison, the person told AFP, would be with the approximately 2,150 operationally deployed strategic US nuclear warheads listed as of last December.
In May 2010, after extensive debate within President Barack Obama's administration, the Pentagon revealed the extent of its nuclear arsenal for the first time.
It said the US stockpile of nuclear weapons consisted of 5,113 warheads, including active warheads ready for deployment at short notice, as well as "inactive" warheads maintained at a depot in a non-operational status.
The new START accord limits still allow for enough weaponry to blow up the world many times over.Obama has described the treaty as a modest step toward "a world without nuclear weapons," but stressed he knew the goal would not be reached quickly and would take "patience and persistence."