Mitt Romney’s criticism of the New Strategic Arms Reduction Treaty (New START) [“Obama’s worst foreign mistake,” op-ed, July 6] raises several concerns about the agreement and its impact. A close reading of the treaty and understanding of its terms, however, should assuage most concerns.

Massachusetts’ former governor asserts that the treaty “impedes missile defense.” In fact, the preamble notes the relationship between offense and defense, a strategic reality that has been recognized for more than 40 years, but the preamble limits nothing. New START’s only constraint on missile defense appears in Article V, which bans placing missile defense interceptors in converted intercontinental ballistic missile (ICBM) silos or on missile-carrying submarines. This prohibits the United States from doing something the Defense Department does not want to do in any case. Gen. Patrick O’Reilly, head of the Missile Defense Agency, testified to the Senate Foreign Relations Committee on June 16 that, if he needs more missile defense interceptors, it would be simpler and cheaper — $20 million less — to build new silos rather than convert ICBM silos.

Romney expresses concern that Russia reserved the right “to walk away from the treaty” if the United States expands its missile defenses. Every significant arms control treaty since SALT I, signed by President Richard Nixon, has contained a provision allowing a party to withdraw if it considers its supreme interests jeopardized. When signing the 1991 START Treaty, Moscow made a similar unilateral statement expressing concern about U.S. missile defense plans; Moscow did nothing when the United States withdrew from the Anti-Ballistic Missile Treaty in 2002 in order to develop new missile defenses.

Contrary to Romney’s assertion that the treaty “empowers a Bilateral Consultative Commission with broad latitude to amend the treaty with specific reference to missile defense,” New START does no such thing. The treaty provides for a Bilateral Consultative Commission to promote implementation of the agreement. Article XV permits that body to make changes to the treaty’s protocol “that do not affect substantive rights or obligations under this Treaty.” Part Six of the treaty protocol says the commission shall discuss how to distinguish missile defense interceptors and launchers from missiles and launchers limited by the treaty. This language does not limit missile defense.

Romney claims that New START has loopholes that favor Russia and notes that the treaty does not specifically mention rail-based ICBMs or ICBM launchers. Russia phased those systems out of its arsenal several years ago, and the factory that built rail-based ICBMs in Soviet times is located in what is now Ukraine. Were the Russians to resurrect a rail-mobile system — Romney does not substantiate the “reports of growing [Russian] interest in rail-mobile ICBMs” that he cites — New START’s definitions of ICBMs and ICBM launchers would capture those systems under the treaty’s limits.

Romney complains that New START attributes each bomber as carrying one warhead when bombers can carry more nuclear weapons. This reflects a long-standing U.S. desire for preferential treatment for bombers, given that their long flight times make them unsuitable for a first strike. Bombers, moreover, have traditionally been an area of U.S. strategic advantage. Just try to find a U.S. Air Force general who would willingly swap the U.S. force of B-52, B-1 and B-2 bombers for the Russian force of Bear and Blackjack bombers.

Regarding the charge that New START does not prohibit ICBMs on heavy bombers: There is no evidence that the Russians plan to put ICBMs on bombers, perhaps because no bomber in the Russian inventory can carry an ICBM.

Romney asserts that the United States will have to “drastically reduce” its number of missiles and bombers. In fact, the United States will have to cut about 130 deployed strategic missiles and bombers to reach the treaty’s limit of 700 deployed systems. U.S. strategic forces are then likely to have an advantage of 100 to 200 deployed missiles and bombers over Russia’s post-treaty force.

Romney is correct that New START does not limit tactical nuclear weapons, where Russia has a significant numerical advantage. But U.S. allies — those most directly threatened by Russian tactical nuclear weapons — support the treaty. The Obama administration has made clear its intent to negotiate limits on tactical nuclear weapons in the next round; nothing suggests that a Senate refusal to ratify New START would make that negotiation any easier.

The New START treaty concerns issues central to America’s national security. As such, the Senate should give the agreement careful scrutiny. But the debate over ratification should be based on the substance of the treaty, not groundless and misleading assertions.