THE BELEAGUERED reformist faction within Bahrain’s ruling al-Khalifa family has good reason to thank the U.S. Congress. Until this month the Obama administration, which has enormous leverage over the Persian Gulf emirate, was blithely ignoring Bahrain’s crackdown on domestic opposition and its failure to implement promised reforms.

Even as the regime staged unfair trials of peaceful opponents in special security courts, dismissed thousands from government jobs for participating in protests and violently repressed demonstrations in restless villages, the administration notified Congress in September that it intended to sell Bahrain $53 million in military equipment, including 40 armored Humvees.

Set aside for the moment the fact that Bahrain, an island nation that hosts the U.S. Fifth Fleet, has no plausible use for armored vehicles other than against its own people. The sale sent the message to the regime’s hard-liners that domestic repression would not damage relations with the United States. Little surprise that, not long afterward, 20 doctors and nurses who had treated injured protesters were sentenced to lengthy prison terms after a grossly unfair trial.

Fortunately, Bahrain’s abuses — documented and denounced by every major Western human rights group — prompted a reaction in Congress. Legislation was introduced to block the arms sales, and a group of five Democratic senators, led by Robert P. Casey Jr. (Pa.), wrote to Secretary of State Hillary Rodham Clinton on Oct. 12 to ask that the sale be put on hold. A separate letter was dispatched by Sen. Marco Rubio (R-Fla.).

The senators got a response. On Oct. 14, the State Department wrote to Mr. Casey to say that the administration would not proceed with the sale until after the independent international commission appointed to investigate the unrest in Bahrain — with the regime’s cooperation — issues its report, scheduled for Nov. 23. Bahrain, meanwhile, was backpedaling: even before the senators’ letters were sent, the doctors’ sentences were nullified and their cases transferred to civilian court. The pro-reform foreign minister traveled to Washington to assure Congress that the commission’s recommendations will be followed.

This is progress — but there is a distinct danger that the promises of the Khalifas and the State Department will prove hollow. The credibility of the commission has been under question ever since its Egyptian-born chief appeared, in an Aug. 8 interview, to preemptively clear the Bahraini government of a policy of using excessive force or torture. The regime has failed to deliver on pledges made by its reformists in previous trips to Washington.

Rather than tying itself to this uncertain process, the United States should set its own conditions for continued good relations with Bahrain. These should include accountability for the torture and killing of protesters; the release of all political detainees; and the initiation of meaningful political reform that enfranchises the country’s Shiite majority. The current status quo in Bahrain is unsustainable; reinforcing it with U.S. military sales would be foolish as well as unconscionable.