This op-ed was originally published by the Los Angeles Times.

A year ago this week, American officials wrapped up a two-day inspection of a Russian strategic missile base at Teykovo, 130 miles northeast of Moscow, where mobile SS-25 intercontinental ballistic missiles are deployed.

Twelve days later, their Russian counterparts wrapped up a two-day inspection at Whiteman Air Force Base in Missouri, home to a strategic bomb wing.

These inspections are noteworthy because they are the last to be conducted under the 1991 Strategic Arms Reduction Treaty, or START, which expired in December 2009. No American inspectors have set foot on a Russian nuclear base since, depriving us of key information about Russian strategic forces.

Worse, if Republicans in the Senate succeed in delaying ratification of the New START agreement — a distinct possibility — it may be months before American inspectors get another look at Russian nuclear weapons.

This profoundly negative outcome would damage U.S. national security and set the cause of global arms control back years.

It would deprive the U.S. of the ability to assess, up close, the status and operations of Russian nuclear forces. It would undermine both nations’ ability to tamp down tensions as they arise. And it would signal to the rest of the world that the nations that hold 90% of nuclear weapons are incapable of taking a leadership role in arms control. This in turn would threaten nonproliferation efforts worldwide.

There are no substantive objections to the treaty. Instead, it is being held hostage to demands that the Obama administration pour billions more into the United States’ nuclear weapons complex, for modernization of weapons and increased spending on facilities and personnel.

Last week, the administration offered to add $4.1 billion to its previous commitment to spend $80 billion on modernization over the next decade.

The fact is, New START — signed on April 9 in Prague, the Czech capital, by President Obama and Russian President Dmitri Medvedev — has been thoroughly vetted in 18 hearings before the Senate Foreign Relations, Armed Services and Intelligence committees. Concerns that have been raised, such as claims the treaty would hinder U.S. missile defense plans or interfere with conventional missile forces, have been debunked. The Senate has done its due diligence and is ready for an up-or-down vote on ratification.

To see what’s at stake, consider the Russian missile base at Teykovo. The Russians have upgraded at least one of the four garrisons there this year, replacing the single-warhead SS-25 ICBMs with new SS-27s capable of carrying multiple warheads, according to Hans M. Kristensen, director of the Nuclear Information Project at the Federation of American Scientists. All without any oversight by American inspectors.

So it’s clear why the New START treaty is strongly supported by our military and national security establishment, including Defense Secretary Robert M. Gates, Joint Chiefs Chairman Adm. Michael G. Mullen and numerous current and former commanders of U.S. Strategic Command and its predecessor, the Strategic Air Command.

The New START agreement will not erode our nuclear capabilities, strategic deterrent or national defense. In fact, as arms-control treaties go, it is modest stuff. It would cut deployed nuclear warheads by 30%, to 1,550 each, and launch vehicles — such as missile silos and submarine tubes — by more than 50%, to 800 each.

These levels are “more than enough … for any threat that we see today or might emerge in the foreseeable future,” said Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff and a former head of U.S. Strategic Command.

During the 15-year lifespan of the old START agreement, the United States conducted 659 inspections of Russian nuclear facilities, and Russia conducted 481 inspections of our facilities.

It would be foolish and wrong to let partisan politics bring this era of cooperation to an end. Worse, it would make us blind to the true size and capabilities of the Russian arsenal. There is no question this would weaken our national security. That would be indefensible.