New START is a done deal. On Tuesday, the Russian Duma gave the green light to the nuclear arms reduction treaty, as the U.S. Senate had more than a month earlier.

There was little doubt the Duma would approve. After all, Moscow’s negotiators got much the better of their U.S. counterparts. But the provisions inserted into Russia’s ratification law reveal that there is no “meeting of the minds” in two key areas: ballistic missile defense and strategic conventional weapons.

The one-sidedness of the treaty was evident early on. Under New START, only the U.S. has to cut its nuclear arsenal. Russia can actually increase its nuclear stockpiles. Defense Minister Anatoly Serdyukov merely confirmed this when he told the Russian Parliament, “The treaty doesn’t constrain us in any way…its parameters considerably exceed our potential today.” He further added that Russia will not have to cut a single delivery vehicle or warhead before it expires on its own. “We will not cut a single unit.”

Aleksey Arbatov, leader of Center for International Security of Russian Academy of Sciences World Economy and International Relations Institute, echoed this analysis saying, “The treaty is undoubtedly advantageous to our country…it is essentially a treaty on limiting the American strategic forces.” Arbatov concluded that the treaty gives Russia “very serious levers of influence both over America itself and over other countries.”

Equally worrisome, the U.S. and Russian ratification instruments reveal two completely different understandings of how New START will affect key nuclear policies. The Russian ratification law insinuates that the treaty preamble, which expresses a damaging linkage between offensive and defensive weapons, is legally binding. The treaty, Moscow says, therefore limits development of American missile defenses.

The Senate’s document, however, memorializes assurances given lawmakers by the Obama administration. It states that the preamble is not legally binding and in no way restricts our missile defense.

Further clouding this vital issue is Moscow’s renewed interest in building missile defenses of its own. General Nikolai Makarov, chief of the Russian General Staff, recently announced that Russia is working to deploy an “impenetrable” missile-defense shield by 2020. The goal: to defend the entire country — an area that covers nine time zones — from all manner of ballistic missile attacks “at any time and in any situation.” How this initiative jibes with the Kremlin’s assertion that the treaty bars such undertakings is anybody’s guess. It does, however, illustrate once again that the Russians do not oppose missile defenses — only U.S. ones.

Another major area in which the Duma’s understanding is at loggerheads with the Senate’s involves strategic conventional weapons — e.g., intercontinental ballistic missiles armed with non-nuclear explosives.

The Duma’s ratification law states that any new type of strategic offensive weapon — whether nuclear or not — cannot be deployed without prior approval by the Bilateral Consultative Commission (BCC), New START’s implementing body. The United States asserts that (1) the treaty covers only nuclear weapons, (2) the treaty would need to be amended to cover conventional armaments and (3) the BCC mandate extends no further than the nuclear weapons addressed in the treaty.

If Moscow incorporates the Duma provisions on missile defense and conventional weapons as “understandings” in its formal ratification document, these sections will directly contradict those in the U.S. version. That should prompt the U.S. to block the exchange of the instruments of ratification needed for New START to enter into force. But will it?

Owen Graham is a research assistant at The Heritage Foundation. Michaela is a researcher at The Heritage Foundation.