The United States now deploys about 2,000 nuclear weapons of various types. Most of these weapons are targeted at their Russian counterparts.

In order to destroy Russia’s nuclear weapons before they could destroy us, the United States relies on options to strike first. Russia knows this, so has incentives to launch its nuclear weapons before our weapons arrive to destroy theirs. In a crisis, both countries would feel great pressure to strike first, which in turn makes both vulnerable to false warnings and other miscalculations.

Neither has done like China and relied on deterrence through retaliation with a relatively small arsenal. China has only about 60 nuclear weapons that could hit the United States, and a policy of no first use. (North Korea, the other potential target of U.S. nuclear forces, may have up to 10 weapons but no missiles that can reach the United States.) Chinese strategists worry, however, that the United States is seeking a combination of nuclear weapons, long-range conventional strike weapons and missile defenses to be able to conduct a disarming first strike against it.

On what basis could the United States object if China and other potential nuclear competitors sought to mimic our nuclear doctrine and build up their nuclear forces so as to threaten first strikes? Would we not rather avoid this? Under what circumstances would the first use of nuclear weapons be the only means of achieving a necessary military objective and be discriminating in their effects? How would the first use of nuclear weapons conform to the high and rigorous standards of proportionality that the United States sets for using force?

These questions are being asked when it comes to drones but not U.S. nuclear weapons.

When the president renews his nuclear agenda in the coming weeks, he should clarify that the only legitimate circumstance for using nuclear weapons would be as a last resort in response to threats to the survival of the United States or if its allies are threatened. He should call on all states to reaffirm the 67-year taboo against the first use of nuclear weapons and the corollary obligation not to threaten the survival of other nations.

As long as nuclear weapons remain, they can be used. And as long as this is the case, “We cannot expect of others what we will not do ourselves.”

George Perkovich is director of the nuclear policy program at the Carnegie Endowment for International Peace.