Further deployment of the US missile defense system in Europe gives Russia the right to withdraw from the New Strategic Arms Reduction Treaty (START), Russian Deputy Foreign Minister Sergey Ryabkov has said.

"START may become a hostage of the so-called US European Phased Adaptive Approach (EPAA)," Ryabkov said at Monday’s meeting of the Expert Council on cooperation between Russia and NATO at the State Duma.

The official noted that Moscow has repeatedly warned its partners that if the scale of the US missile defense system creates a threat to Russia’s strategic nuclear forces, Russia has the right to withdraw from the agreement. That would be considered “an exceptional circumstance” mentioned in Article 14 of the New START.

He added that Russia will have to take responsive measures if the US and NATO develop their missile defense shield without taking Moscow’s opinion into account.

"In this situation, we will have to take the necessary measures to restore the disrupted balance of power," Ryabkov said, cites Interfax.

The official also observed that Moscow is disappointed over Washington’s denial to give legal guarantees that the US missile defense system will not be targeted against Russia.

"We are disappointed with the reaction of Washington; this is a negative reaction," he said.

The historic agreement – the New START – was signed by Presidents Barack Obama and Dmitry Medvedev on April 8, 2010, in Prague.

On Saturday, President Dmitry Medvedev sent letters to Russia-NATO Council members in which he reaffirmed Moscow’s readiness to contribute to maintaining strategic stability and security by creating a joint missile defense system in Europe.

“The Lisbon summit of the Russia-NATO Council on November 20, 2010, opened up opportunities for building strategic partnership based on the principles of equality, indivisible security, mutual trust, transparency, and predictability," the president’s letter reads, the Kremlin press service reported on Saturday.

Medvedev confirmed Russia’s readiness – voiced at the summit – to take a share of responsibility for maintaining strategic stability and security, including through the creation of a joint missile defense system in Europe. He underlined that the system could only be truly efficient and viable if Russia participates in the project as an equal member. The Russian President stressed the need for guarantees that the shield being deployed in Europe will not undermine strategic stability and will not be aimed against one of the sides.

Almost half-a-year on after Moscow was officially invited to participate in the missile defense program, the sides have not managed to iron out differences in their views on the planned system.

Moscow said it was ready to assume protection of its sector in Europe from a missile threat in the framework of the so-called “sectoral” approach put forward by Medvedev. The general idea is that Europe would be divided into sectors and each side – Russia and the Western partners – would defend their sector of responsibility. Moscow has also warned that if no compromise is found on missile defense and the West ends up building its own shield, Russia would have no choice but to respond with military measures.

On May 4, at the meeting of commanders of the general staffs of the Russia-NATO Council 29 member states in Brussels, Russia’s General Nikolay Makarov said that Moscow would insist that the alliance would guarantee that its European missile defense would not pose a threat to Russia’s strategic nuclear forces.

"We intend to seek firm guarantees on de-targeting missile defense against Russia's nuclear potential. We will wait for proposals from NATO. We hope that our European colleagues will understand us", Makarov said. "We cannot create the security situation in Europe depending on the Russian-US agreements as it was during the Cold War times," he added, cited Itar-Tass.

The gathering took place shortly after the US announced its plans to deploy interceptor missiles in Romania, which raised serious concerns in Moscow.

Russia’s Deputy Defense Minister Anatoly Antonov said on Friday that the Brussels talks brought no breakthrough.

“We cannot watch indifferently as the US is deploying near our borders elements of its missile defense system, which can reach as far as the Urals,” he told journalists in Moscow. Russia is being told that its security would only benefit from it as Americans would be able to intercept missiles over the Russian territory. However, Moscow is not happy with such an approach as it can provide its national security itself, he added.