The Obama administration has failed to complete the negotiation of a treaty to replace the Strategic Arms Reduction Treaty (Start), which expired on Dec. 5. The two superpowers are now in unchartered waters.

Moscow and Washington have stated that Start still applies voluntarily. This is false. First, without the consent of the U.S. Senate, expired treaties are null and void. Second, the Russians already kicked out U.S. inspectors, thus scrapping a key provision of the now-dead treaty. Third, on Tuesday, Dec. 29, Prime Minister Vladimir Putin upped the ante, linking U.S. missile defenses with the treaty signature. Speaking in Vladivostok later that week, Mr. Putin warned against U.S. "aggressiveness" and disruption of the nuclear balance in case the Obama administration deploys missile defenses.

As competition between Mr. Putin and President Dmitri Medvedev for the 2012 presidential nomination is rising, Mr. Putin may be denying his former protégé a prestigious feather in his statesman's cap.

The official talks will restart in Geneva, possibly as early as next week. And the American side also appears circumspect. The U.S. Senate is concerned with the future of the Start follow-on treaty. Senators worry that the Obama administration may be making concessions to Russia that are detrimental to U.S. national security. On Dec. 16, 41 senators signed a letter to President Obama, saying that they will oppose the new treaty if the United States gives up nuclear modernization. Thus, the 67 vote supermajority necessary for ratification is far from secure.

Supporters of missile defense, nuclear modernization and prompt global strike intercontinental ballistic missiles with conventional warheads would oppose the treaty if it undermines their priorities.

The Kremlin feels it has a winning hand in the nuclear bargaining as the follow-on treaty is considered more important to the United States than Russia. The White House already ceded deployment of a stationary missile defense in Poland and the Czech Republic and has agreed to pull U.S. inspectors from a missile factory in Votkinsk, Russia. The removal will make it impossible to monitor production of Russia's new RS-24 mobile multi-warhead ICBMs. This missile will be the mainstay of Russian strategic forces by 2016. Thus, the stronger party starts looking like a loser.

Preoccupation with the Start follow-on treaty is a major part of Mr. Obama's effort to "reset" relations with Russia. The completion of the Start follow-on, as well as the ratification of the Comprehensive Nuclear Test Ban Treaty by Congress, are seen as a key stepping stone of "getting to zero" -- achieving a world without nuclear weapons.

The Russians, however, quietly scoff at Mr. Obama's goal. While the Russian government publicly champions the U.S. nuclear disarmament effort, Russia's military and security elite deride it. "Russia will develop offensive weapons -- because without them there is no other way to defend our country," Mr. Medvedev said in the recent TV interview.

Moreover, Russian nuclear policy and statements clearly reveal an abiding commitment to nuclear weapons. The U.S. national leadership and arms control negotiators should examine the Russian nuclear doctrine and policy as they are, not as they want them to be.

Russia is boosting the role of nuclear weapons in its national security strategy and doctrine. Russia's nuclear doctrine considers the United States its "principal adversary." With deficiencies in its conventional forces and difficulties procuring and deploying high tech weapons, Russia will increasingly rely on nuclear weapons, including first-use use in local conflicts, such as with Georgia last year. This is what Russia's National Security Council Secretary , General Nikolay Patrushev recently announced.

Moreover, Russia has 3,800 tactical nukes, which were not included in the follow-on treaty. And in the recent military maneuvers in Belarus, the Russian Army simulated an invasion of Poland -- with 900 tanks and fired three nuclear missiles at the "enemy."

Mr. Putin has repeatedly announced that despite the economic crisis, the Russian government will continue major funding for advanced military equipment, including nuclear weapons modernization. Russia's military-industrial complex is busy developing high-precision and low-yield deep-penetration nuclear weapons. But the Russians are also demanding the halt to U.S. nuclear modernization, which the bipartisan Perry-Schlesinger Commission recommended to the U.S. Congress and is necessary to maintain an effective deterrent.

Lastly, the U.S. intelligence community advised Congress that Russia is currently in violation of Start, as well as other arms control and nonproliferation agreements. The Obama administration's broader agenda to "get to zero" appears to have compromised the treaty negotiations. This has caused Senator Jon Kyl, Republican of Arizona, to accuse the administration of arms control malpractice.

To put it simply, the new treaty must not compromise U.S. or allied national security. It should not limit U.S. missile defenses or nuclear modernization. The U.S. should oppose a Russian offensive nuclear posture, and counter the further lowering of the nuclear threshold. The United States should pursue a "protect and defend" strategy, which includes a defensive nuclear posture, missile defenses and nuclear modernization.

Ariel Cohen, Ph.D., is Senior Research Fellow in Russian and Eurasian Studies and International Energy Security at the Allison Center of the Katherine and Shelby Cullom Davis Institute at The Heritage Foundation.