U.S. nuclear arms inspectors recently discovered that Russia is violating the New START arms treaty by improperly eliminating SS-25 mobile missiles, American defense officials said.

The violations were discovered during an on-site inspection carried out in Russia in April, said officials familiar with details of the inspection.

During the recent visit to a Russian missile base, U.S. technicians found critical components of SS-25s—road-mobile, intercontinental ballistic missiles—had been unbolted instead of cut to permanently disable the components.

Additionally, American inspectors were unable to verify missiles slated for elimination had been destroyed. Instead, only missile launch canisters were inspected.

As a result, inspectors were unable to determine if the missiles were properly eliminated as required by the 2010 arms treaty, the officials said.

Additionally, the inspectors found that Russian missile forces had improperly displayed missile components slated for destruction by failing to leave them in the open for monitoring by so-called national technical means of verification, a euphemism for spy satellites and other sensors used in monitoring arms accords.

On-site inspectors also reported they were unable to verify that Russia had completed all New START treaty cuts to launchers declared eliminated by Russia between 2011 and 2015.

"Russia will meet their treaty elimination goals by using empty launchers from retired and retiring missile systems," said one official. "They’re basically cutting up launchers that don’t carry missiles anyway."

Disclosure of the New START treaty violations is a further setback for the Obama administration’s arms control agenda. The administration has made arms agreements with Russian aimed at cutting nuclear forces a priority. Arms talks have been suspended since Moscow militarily annexed Ukraine’s Crimea in 2014.

Asked about the April verification problems, State Department arms verification bureau spokesman Blake Narenda declined to discuss the matter, citing treaty secrecy rules.

"The New START treaty forbids releasing to the public data and information obtained during implementation of the treaty," Narenda said in a statement.

"This would include any discussion of the results of inspection activities undertaken by the United States or the Russian Federation," he said. "However, both sides continue to implement the treaty in a businesslike manner."

On Capitol Hill, House Armed Services Committee Chairman Mac Thornberry said the potential New START verification problem highlights the larger issue of the Obama administration’s poor record in pressing Russia to abide by its treaty obligations.

"Whether it's Russian violations of the Open Skies Treaty, the Biological and Chemical Weapons Conventions, or multiple violations of the INF treaty, this administration has proven singularly unconcerned with arms control compliance," Thornberry told the Free Beacon.

"Never having been made to pay a price, why wouldn't Putin conclude that violations of the New START treaty would go unpunished as well?" he said.

John Bolton, former U.S. ambassador to the United Nations and a former State Department undersecretary for arms control, said the latest Russian treaty issue raises questions about whether Moscow may have helped Iran to circumvent treaties.

"Russian denials, obstructionism, and outright deception are nothing new in their efforts to prevent effective verification of arms control treaties," Bolton said. "And just imagine what Moscow has taught Tehran."

Mark Schneider, a former Pentagon strategic nuclear policymaker, said the New START arms accord has serious verification shortcomings.

"The New START treaty is a verification disaster area and Russia has a long history of violating substantive and verification provisions of strategic arms control agreements," said Schneider, a senior analyst at the National Institute for Public Policy.

Schneider, former Pentagon director for strategic arms control policy, said Russia has avoided complying with its treaty commitments. "They have violated all of the major arms control treaties and will continue to do so because we impose no penalties," he said.

New START provisions for eliminating solid-fuel missiles like the SS-25 call for crushing the first stage rocket motor or cutting it in two equal parts.

"If Russia has not done this, the missiles would not have been removed from accountability," Schneider said. "The requirement for cutting, crushing, or flattening is intended to prevent the reuse of the rocket motor casings to produce new missiles. There is no other reason to violate this provision of New START, except perhaps to sell them to rogue states."

Schneider said the elimination procedures for New START are less stringent than under the earlier START accord that allowed inspectors to witness the elimination of all mobile ICBMs.

"This is not the case under New START," he said. "For solid-fuel ICBMs, including mobile ICBMs, inspectors do not have the opportunity to observe eliminations. Instead, they are allowed to view a portion of the remains from eliminations."

Mobile launchers under New START also are eliminated by cutting erector-launchers, leveling supports, and mountings from the mobile chassis and removing launch support equipment, including instruments.

Also, Russia is required under the treaty to display old mobile launchers for spy satellites to verify their elimination and to permit U.S. inspectors to verify the missile destruction within 30 days.

The Obama administration’s record for responding to arms cheating by Russia is weak. The State Department, which is in charge of monitoring treaty compliance, hid Moscow’s violation of the 1987 Intermediate-Range Nuclear Forces Treaty for several years to avoid upsetting its arms control agenda.

The INF violation was finally made public in 2014 after prodding from Congress in a State Department report that said the violation involved Russia’s development of illegal ground-launched cruise missiles.

According to the State Department web site, there have been four "Type 2" on-site inspections since February under New START. Type 2 inspections are those used for confirming missile eliminations like those used for the SS-25.

The location of the April treaty inspection could not be learned.

Known locations where Russia has deployed SS-25s at bases include Yoshkar-Ola, Vypolzovo, Irkutsk, and Barnaul, according to the Russian strategic nuclear forces blog.

In February, Secretary of State John Kerry hailed the fifth anniversary of the New START treaty as a "landmark" arms control accord.

"New START is more important now than when it went into effect. It gives us the confidence and level of oversight we need— and could not otherwise have— by allowing U.S. inspectors unprecedented access to Russian nuclear facilities," Kerry said.

However, Russia has voiced less enthusiasm for the treaty. Russian Deputy Foreign Minister Sergei Ryabkov said in April that New START will be an "end document" for U.S.-Russian arms control relations.

Asked if New START is a final accord, Ryabkov told Interfax, "Saying ‘final' is not fashionable today. I would say that this document will obviously become an end document because, indeed, it has an end position on this scale of coordinates, where the time scale goes to the right and the quantity scale goes upwards, in other words, it is the quantity of weapons slated for limitation."

The treaty calls for both Washington and Moscow to pare their nuclear arsenals to 700 deployed land-based and sea-based missiles and heavy bombers, 1,550 deployed warheads, and 800 non-deployed launchers and bombers.

Last Saturday, Anita Friedt, principal deputy assistant secretary of state for arms control verification and compliance, gave a speech that gave no suggestion there are problems with New START verification.

"Buttressed by this robust verification architecture, New START treaty implementation is proceeding well and both the United States and Russia are expected to meet the treaty’s central limits when they take effect in February 2018," she said.

However, Friedt said New START verification measures, despite their intrusiveness, "may not be sufficient for effective verification in the future."

The House fiscal 2017 defense authorization bill contains a provision that if passed would prohibit the Pentagon from spending any funds to implement New START until Pentagon officials reported to Congress about the treaty’s impact on critical defense capabilities.

The provision would block funding until the defense secretary and chairman of the Joint Chiefs of Staff assessed the treaty’s impact on U.S. rapid reload of ballistic missiles and the impact of the treaty on U.S. deterrent strategy.

The bill also would require an assessment of the threat posed by non-treaty-limited nuclear or strategic conventional systems to the United States and American allies and of the risk posed by Russian arms violations. It would require an explanation of why continued treaty implementation is in U.S. national security interests.