SIX WEEKS after Egypt’s coup, the military-backed regime that aspires to control the country faces a critical decision. Tens of thousands of followers of ousted president Mohamed Morsi are encamped in two Cairo squares; some are building defensive walls and there are reports of cached weapons. Police and other security officials are reportedly ready to forcibly break up the camps but are opposed by some of the civilians appointed by the military to an interim cabinet, who, along with Western diplomats, are pressing for restraint. On Monday, Egyptian media reported that a possible move against the camps had been deferred, providing a slight opening for a political solution.

All who favor a return to stability and democratic government in Egypt, including the Obama administration, must now exert maximum pressure on the Egyptian military to refrain from the use of force. There is little question that any attempt to disperse the protest camps would lead to considerable bloodshed: Egypt’s security forces, which have already killed hundreds of unarmed civilians since the July 3 coup, lack the capacity to disperse protestors by non-lethal means. A violent confrontation would greatly reduce the already diminishing possibility of a political settlement between the military and Mr. Morsi’s Muslim Brotherhood, and possibly drive underground a movement that continues to have the support of millions of Egyptians.

The Obama administration purports to accept the de facto regime’s assertion that it is returning Egypt to democracy. But a legitimate democracy cannot be built on mass bloodshed or the repression of the country’s largest political movement. Even while refraining from action against the protest camps, the interim cabinet appears to be excluding Islamists. It continues to hold Mr. Morsi and other senior Brotherhood leaders incommunicado on dubious charges of espionage and murder.

The interim government’s representatives claim that the Muslim Brotherhood has been intransigent, demanding that Mr. Morsi be returned to office. Yet, as a joint U.S.-European Union statement, following last week’s failure of mediation efforts, said, “the Egyptian government bears a special responsibility to begin this process” of breaking the political stalemate. It could do so by releasing Mr. Morsi and declaring that it will not use force against the camps or any other protests while they remain peaceful.

The United States, too, has a special responsibility to work for a political settlement that restores democracy in Egypt, given its long-standing ties to the armed forces and $1.3 billion in annual military aid. U.S. officials lament their apparent inability to influence the generals, who rejected Washington’s urgings against the coup and now ignore its proposals for confidence-building measures and political compromise. But the Egyptian reaction is the logical result of the Obama administration’s failure to act on its previous warnings by suspending aid, as U.S. law requires. What’s called for now is a clear warning from the highest level: The further use of force against the Muslim Brotherhood will lead to the immediate suspension of U.S.-Egyptian military cooperation.