In today’s Wall Street Journal, Steven Pifer responded to Senator Jon Kyl’s (R–AZ) op-ed that argued that President Obama should refuse to provide written assurances to Russia that compromise America’s ability to defend itself.

Pifer’s complaint with the Senate Republican Whip’s argument is that “an assurance could open a path to a cooperative NATO-Russia missile defense.” Pifer misses the point.

Missile defense is inherently defensive in nature and poses no offensive threat to any country. The Russians want assurances from the U.S. that U.S. missile defenses will not ever have the ability to intercept Russian missiles headed toward American cities. Pifer believes that since the U.S. missile defense system is not currently able or intended to defend against Russian missiles, which the Senator readily admits, then it would do no harm to make this the permanent status quo.

Here’s the problem with that: Russia has the capability to pose a strategic nuclear threat to the U.S. It currently does not have the intent to employ strategic nuclear weapons. But intentions can change.

The U.S. should reserve the right to build up or alter its national security systems and strategies as it deems necessary for its own security. Even if an assurance (such as the one Pifer would have the U.S. provide to Russia) would please Moscow, it would do nothing to further U.S. national security objectives. Indeed, it would only further Russia’s objectives.

Arms control can be a useful means to achieve security aims, but it should never come at the expense of security.

According to press reports, just days ago Russia launched a new intercontinental ballistic missile, broadcasting to its neighbors and the U.S. that it is improving its offensive arsenal. Yet we never heard a peep from the U.S. President or arms control advocates requesting assurances from the Russian Federation that its missiles would not be used against the U.S.