In the wake of the Senate’s consent to New START, Washington’s wonkdom is focusing on ballistic missile defenses and tactical nuclear weapons. The reasons why are clear enough: The Senate has laid down markers calling for discussions on Russia’s non-strategic nuclear weapons and the deployment, as promised, of planned theater missile defenses. The former will open a can of worms and the latter will raise hackles in Moscow, which remains hypersensitive about BMD.

The next treaty is usually more complicated and harder to negotiate than the last, and the successor to New START will probably be no different.

If we’re going to expend a great deal of effort on new negotiations, setting priorities might be helpful. In my view, tactical nuclear weapons and BMD pale in strategic significance to a dangerous competition between major powers in space. U.S. citizens are very dependent on satellites for their national, economic, and personal security. What happens in space is far more consequential than the size of the Russian stockpile of non-strategic nuclear weapons or how many Aegis cruisers the Navy deploys.

Don’t get me wrong: I would like to count and reduce the stockpile of Russian tactical nuclear weapons. But what matters most in any strategic competition, crisis, or limited war is a crossing of the nuclear threshold – not the range of the nuclear weapon delivery vehicle that crosses it. Russia’s still bloated, greatly reduced stockpiles of short-range nuclear weapons pose a potential threat, but their use would result in great pain and no benefit to Moscow. Besides, the likelihood of a nuclear exchange between Moscow and NATO is as low as it has ever been during the Nuclear Age.

The strategic significance of BMD is also limited, notwithstanding the hyperventilation of its die-hard supporters and opponents. Even the most enthusiastic U.S. administrations have been constrained by technical, cost, and political realities surrounding BMD. Successive administrations with very diverse political orientations have all landed on approximately the same place: a modest national insurance policy against rudimentary, trans-oceanic threats, and far more concerted efforts in regions where U.S. forces, friends and allies face outlier regimes equipped with ballistic missiles. Technological advancements, flight tests, and smart theater missile defense architectures can help reinforce the NPT without threatening the Russian and Chinese deterrents.

In contrast, certain actions in space can have profound implications for national security and deterrence, which depend on the ability of various satellites to perform as planned. A growing number of nations now have the ability to interfere with these satellites. Space is becoming, as the Pentagon likes to say, more congested, competitive, and contested. A competition in space characterized by thinly disguised or overt anti-satellite weapon tests, and a space environment with weak norms governing space traffic management and debris mitigation, will have far greater strategic significance than how many tactical nuclear weapons major powers possess, or how many theater missile defense interceptors they deploy. The way major powers relate to each other in space is intertwined with how they relate to each other here on earth. If the United States and Russia do not reach agreement on rules of the road for space, nuclear dangers will rise, and prospects for the next New START will become more remote. More importantly, behavior in space will shape U.S.-Chinese relations, especially since Beijing doesn’t talk very much about nuclear weapons.

The Obama administration can no longer afford the luxury of pursuing one set of strategic negotiations at a time. It appears to be gearing up for the less important one.