It now appears likely that the Russian Duma will attach an understanding to the new strategic nuclear arms control treaty with the U.S., known as New START, that specifically rejects the U.S. Senate’s understanding that Russia has no grounds for using New START to impose general limits on U.S. missile defense options. The Duma is scheduled to continue consideration of the treaty next month.

Such an action by the Duma would confirm the suspicions of a number of Senators, led by John McCain (R–AZ), that the Russian government would point to language in New START’s preamble as a means of limiting U.S. missile defense options. This language re-establishes the “link” between strategic offensive arms and missile defenses that was broken by President George W. Bush in 2002, when the U.S. withdrew from the Soviet-era Anti-Ballistic Missile Treaty, which imposed severe restrictions on the U.S. missile defense program. Accordingly, McCain offered an amendment to New START in the Senate to delete this language in the preamble. The amendment was defeated on the basis that the language in the preamble is not legally binding.

As a weaker alternative to the McCain amendment, Senators McCain, Bob Corker (R–TN), and Joe Lieberman (I–CT) attached an understanding on December 22 that specifically rejects the Russian claim that the language in the preamble is legally binding. Apparently, the understanding the Duma will consider will clearly and unequivocally reject the understanding attached by the Senate.

The Heritage Foundation has expressed concerns about the negative impact New START’s provision in the preamble could have on the U.S. missile defense program and pointed out during Senate consideration of the treaty that the Senate had the option to strike this language. The Senate rejected this option and chose to adopt the understanding.

An explicit action by the Duma to reject the Senate understanding raises two fundamental questions, one of which could be very explosive. The first is whether the two diametrically opposed understandings will bar the exchange of the instruments of ratification and entry into force of New START. The Obama Administration is legally bound to include the Senate understanding in the U.S. instrument. It cannot simply walk away from it. While the Administration could try to ignore the understanding in the Russian instrument of ratification, this runs the risk of the U.S. being charged by Russia with material breach of New START if it undertakes steps to improve U.S. missile defense capabilities. In reality, the language of the two understandings will reveal that there is no agreement between the parties on an issue that is essential to the treaty. The honest thing to do would be for both parties to acknowledge this and not exchange the instruments of ratification.

The second and more explosive issue is what would happen if the Russians reveal relevant portions of the treaty negotiating record that show that U.S. negotiators pledged to limit the U.S. missile defense program in accordance with the logic of the language in the preamble. It is all but certain that the understanding attached by the Senate contradicts such a pledge, if it was provided. Accordingly, such a revelation by Russia would constitute compelling evidence that the Obama Administration misled the Senate. Compounding the problem for the Administration will be the fact that it withheld the negotiating record from the Senate, despite demands from some Senators. The Heritage Foundation on took the position that access to the treaty negotiating record should have been provided to the Senate.

In short, the impending action by the Russian Duma may well raise fundamental questions about the viability of New START. These include whether there is no proper agreement between the parties on the issue of missile defense and whether the basis for the Senate granting consent to ratification does not correspond to the requirements of the treaty.