IF THERE is an Exhibit A for how the ascent of the Trump administration is leading to the deterioration of human rights in other countries, it is Bahrain — an island kingdom in the Persian Gulf that is the host of the U.S. 5th Fleet. Since 2011, when its majority-Shiite population revolted during the Arab Spring, the Sunni monarchy has engaged in serial campaigns of repression, interspersed with gestures at liberalization aimed at appeasing the United States.

In September, fed up with Bahrain’s backtracking on the imprisonment of dissidents and refusal to engage with peaceful opposition parties, the Obama administration conditioned a $3 billion sale of 19 F-16 warplanes to the country on a private list of human rights concessions. They were steps U.S. officials believed Bahrain could fulfill without risk — such as the release of prominent human rights advocate Nabeel Rajab.

The regime of King Hamad bin Isa al-Khalifa did not comply. Instead it waited for the results of the U.S. presidential election. When Donald Trump won, it appealed for the F-16 sale to go forward without conditions — and meanwhile launched a new crackdown on opponents at home. In the past few weeks, the government moved to dissolve a moderate, secular opposition party, restored the power of a domestic intelligence agency to make arrests, and pushed a measure through parliament authorizing military trials of civilians.

Despite these brazen measures — the last two of which reverse reform steps Bahrain previously took in response to U.S. criticism — the Trump administration appears to be preparing to go forward with the F-16 sale. Congressional sources say they believe that Secretary of State Rex Tillerson and Defense Secretary Jim Mattis have agreed to divorce political conditions from military cooperation with Bahrain and other Persian Gulf allies, and that the State Department may soon send notification of the F-16s to the Senate Foreign Relations Committee. That would please Chairman Bob Corker (R-Tenn.), who has publicly called for the deal to proceed without conditions.

Other members of the committee, from both parties, remain disturbed by Bahrain’s behavior and by the prospect of an unconditional sale. Ranking Democratic member Benjamin L. Cardin of Maryland raised the issue in a recent phone call with Mr. Tillerson. They are right: The United States has considerable leverage over the Gulf emirates, and it is wrong not to use it to check abuses of human rights. The problem is not just a moral one; the Bahraini regime’s abuses risk further destabilizing the country and triggering a sectarian conflict that nearby Iran could exploit.

It is difficult for Congress to block an arms sale — it must pass a resolution within 30 days of a formal notification. But Mr. Cardin and other Foreign Relations Committee members should insist that before going forward with the Bahrain deal, the administration come up with a strategy to reverse the ongoing repression. Mr. Rajab and other nonviolent opponents should be released and peaceful opposition political parties allowed to organize. If the Trump administration signals toleration for the crackdown, it will betray liberal reformers across the region.