Ten years ago last week, the Senate rejected the treaty for a global ban on nuclear tests. In April, President Barack Obama promised to “immediately and aggressively pursue U.S. ratification.”

Proliferation threats like Iran make U.S. ratification more urgent and a smart global security strategy. After the U.S. and China ratify, the major powers will have another tool for impeding Iran’s nuclear ambitions. Because China’s ratification is linked to the timing of U.S. ratification, the United States must act first.

In light of recent revelations and consternation about Iran’s pursuit of a nuclear weapons capability, the global test ban is a critical tool. Iranian ratification is both a confidence-building measure and an obstacle to nuclear weapons development. A would-be nuclear weapons state requires nuclear tests to have confidence that its weapons work and can be deployed as deliverable nuclear warheads. States in pursuit of prestige also use nuclear tests to announce their capabilities.

Banning tests undercuts the drive for prestige, as it becomes an unlawful activity. By legally committing itself to the global norm against nuclear tests, Iran could reduce concerns about its nuclear program. Not doing so increases the skepticism from countries that until now have kept an open mind about Iran’s “nuclear file.” The U.S. would be in a stronger position to make this demand and to translate that skepticism into support for other enforcement measures if it ratifies first and soon.

Opponents to ratifying the test ban are undercutting U.S. security. The Comprehensive Test Ban Treaty would freeze currently inferior arsenals in Northeast Asia, South Asia and the Middle East, and forbid these states from conducting tests needed to improve their arsenals. With the CTBT in force, global and national capabilities to detect and deter possible clandestine nuclear testing by other states improve greatly. Entry-into-force is essential to making the short-notice, on-site inspections in states of concern possible. These outcomes are in American interests.

Critics also ignore tremendous technological and scientific progress. A lot has changed in the decade since the U.S. Senate considered the global test ban. The CTBT’s global alarm system gives new confidence that clandestine nuclear tests will be detected, as demonstrated by two North Korean tests.

The last decade has also proven that the U.S.’s 17-year nuclear test moratorium has not jeopardized, in the words of Secretary of State Hillary Rodham Clinton, “the safety, security, or credibility” of the U.S. nuclear arsenal.

Confidence in the nuclear arsenal depends largely on advances in super computing. Super computers used today for nuclear weapons simulations are over 10 times faster than the goal put forward in 1999 and will be 10 more times faster by 2012.

Considering these advancements, opposition to ratifying the CTBT is equivalent to handcuffing the U.S. in its efforts to prevent other nuclear weapon states from emerging. Denying the U.S. a key tool in that fight makes no sense. To date, the U.S. has contributed financially, advanced technologically, but has reaped none of the political or lasting security benefits. This is a mistake that is further complicated by the growing demand for the CTBT.

One hundred-fifty countries have ratified the global test ban, over 180 have signed it, and eight more states, aside from the U.S., are required to ratify before the treaty’s benefits can be fully exploited. China will likely ratify right before or just after the United States does. Indonesia has promised to immediately ratify after the U.S. The power of the American example is still strong. Consequently, U.S. ratification will trigger a decrease by a third the number of holdout states.

The strategic context for the remaining states will also change, and they will be more susceptible to international pressure. The good news is that the U.S. is not alone in efforts to get the other hold out states to ratify. Last month at the U.N., 150 countries agreed to steps to do just that. Pressuring Iran to abide by the CTBT is the kind of measure that the rest of the world will get behind and will actually directly impact the core problem.

Opponents of the CTBT who ask what the U.S. will receive in return for ratification forget that the rest of the world already gave what the U.S. sought when they agreed in 1995 to extend the Nuclear Non-Proliferation Treaty indefinitely. It is the United States that has not lived up to its end of the NPT bargain. It’s time for America to keep its promise.