PRESIDENT OBAMA has backed a NATO intervention to stop crimes against humanity in Libya, and he has denounced as “abhorrent” the bloody crackdown in Syria. But the president and his administration remain mostly silent about another ugly campaign of repression underway in the Arab world, in the Persian Gulf emirate of Bahrain. The reason is easy to understand: Bahrain hosts an important U.S. naval base, and the wave of arrests, extrajudicial killings and media censorship has been strongly supported — if not ordered — by neighboring Saudi Arabia.

The administration’s silence, like the crackdown itself, is nevertheless counterproductive. The repression, which is focused on Bahrain’s majority Shiite population, is likely to foment the very problem that its advocates seek to prevent: a sectarian uprising in the region that could be exploited by Iran.

Though the Saudis and Sunni hard-liners in Bahrian’s ruling al-Khalifa family insist on describing it in sectarian terms, Bahrain’s unrest began very differently — as a mass, mostly peaceful pro-
democracy movement like those elsewhere in the region. After an initial attempt at repression, the regime, encouraged by the Obama administration, tried negotiating with the opposition. The relatively progressive crown prince proposed talks on a series of democratic reforms, including granting more power to an elected parliament.

But on March 15, Saudi troops, in concert with other Gulf States, invaded Bahrain, nominally at the invitation of the government. A protest encampment at a traffic roundabout was cleared by force, and the monument in Manama’s Pearl Square that was its centerpiece was torn down. In the past month, police and other security forces have killed at least 15 people and arrested hundreds. Reports of beatings and torture of those arrested are abundant, and at least three detainees have died in custody.

The arrested have included people suspected of participating in protests as well as prominent human rights activists and opposition political leaders. The editor of the country’s leading independent newspaper was forced to resign. According to Human Rights Watch, “abuses have escalated in recent weeks, including beatings at checkpoints by masked uniformed and plainclothes men, nightly raids on homes of perceived activists and demonstrators, and the forcible removal from hospitals of badly injured patients who appear to have sustained injuries from police.”

The Obama administration opposes the crackdown; it has tried to strengthen the regime’s reformists and has pushed for a return to negotiations. But apart from an initial critique of the use of force by Secretary of State Hillary Rodham Clinton and one statement about the arrest of a blogger, the administration has remained silent. Worse, Defense Secretary Robert M. Gates appeared to bolster the Saudis’ hard line during a visit last week to Riyadh, saying that “we already have evidence that the Iranians are trying to exploit the situation in Bahrain.”

No doubt Tehran will benefit from sectarian conflict in a Persian Gulf state. But the regime’s crackdown makes that strife more rather than less likely. Instead of quietly tolerating the repression, the United States should be pushing back with both Bahraini and Saudi leaders — and letting the rest of the region know where it stands.