WASHINGTON -- The U.S. government said that Russia has increased the number of strategic warheads deployed on ballistic missiles, despite a 5-year-old treaty that mandates cuts to both countries’ nuclear arsenals.



The numbers by the U.S. State Department’s arms control and treaty verification bureau, which were released late on April 1, were likely to deepen concerns among U.S. lawmakers about Russia’s military intentions.



Under President Vladimir Putin, Moscow has spent heavily in recent years to upgrade weaponry, equipment, and training for its armed forces, including new ballistic missile submarines and other missile systems. The payoff for those investments has been showcased in Moscow’s interventions in Ukraine and, more recently, in Syria, where new jets and cruise missile systems have been on display.



The State Department figures showed that Russia had nearly 200 more warheads deployed now, as compared to 2011, when the treaty known as New START went into force.

The United States, by contrast, has dropped its warhead count below the limits set by New START, two years before the full limitations are supposed to take effect.



The 2010 treaty requires both sides to reduce deployed warheads to 1,550 by February 2018.



Hans Kristensen, a well-known arms control researcher at the Washington-based nonprofit Federation of American Scientists, attributed the uptick in Russian warheads likely to a third new model ballistic-missile submarine that went into service last year.



“But Russia is nonetheless expected to reach the treaty limit by 2018,” he wrote in a blog post.

Since Russia’s annexation of Ukraine’s Crimea Peninsula, and the conflict in eastern Ukraine, the issue of Russian compliance with the arms-control treaties has attracted new scrutiny by lawmakers in Congress.



Republican lawmakers, in particular, have been upset by the U.S. announcement in 2014 that Russia was in violation of another key Cold War agreement: the Intermediate-Range Nuclear Forces Treaty of 1987.



The treaty, known as the INF, eliminated an entire class of cruise missiles from Europe.



The State Department has said repeatedly that Moscow was testing new ground-launched cruise missiles, in violation of INF limitations. Moscow has both denied that assertion and argued that the Washington was itself in violation for deploying antimissile radar and missile interceptors in Europe.



At a hearing last month of the Senate Armed Services Committee, lawmakers grilled the State Department’s lead arms control official, Rose Gottemoeller, about the INF violation.



One Republican senator, Bob Corker, asserted that the White House may have known of the INF violations, and possibly misled Congress, even as it was trying to finalize negotiations with Moscow over the New START treaty.



Gottemoeller denied that U.S. intelligence knew of potential INF violations prior to the Senate vote to ratify New START in 2010.



In contrast to previous statements, she also suggested that there had been progress in U.S. efforts to push Russia on complying with the INF.



“I see some progress in Russia's willingness at the highest level to recommit to the treaty now, and we’re looking forward to moving expeditiously in 2016 to try to make some progress on this difficult matter,” she told lawmakers, according to a transcript of the March 17 hearing. “But I cannot duck the fact that it has been a very difficult negotiation.”