EGYPT’S MILITARY rulers, who pledged in February to replace the autocracy of Hosni Mubarak with a liberal democracy, have taken another big step toward betraying that promise. On Tuesday the interim government appointed by the generals disclosed plans to impose a 22-article charter of “principles” that would bind a constituent assembly as it drafts a new constitution. Among other things, it would prohibit parliament from supervising the military’s budget, which would remain secret, and give the armed forces a check on any government by declaring them the protector of “constitutional legitimacy.”

The military also radically revised plans for the constitution-drafting assembly. Under the new plan only 20 of its 100 members would come from the parliament to be elected beginning later this month; the other 80 would be chosen by the military. This provision, which violates a charter approved by Egyptians in a national referendum in March, was accompanied by others giving the army the right to reject any constitutional article it disapproves of and to dissolve the constituent assembly if it does not produce a document acceptable to the generals in six months.

If sustained, the new “constitutional principles” will go a long way toward preserving the military-backed regime that has ruled Egypt since 1952 — and that Egyptians thought they had ended with their 18-day uprising. It will render the scheduled democratic elections virtually meaningless, since those elected will not have the right either to govern the country or prepare its new constitution. And it could prompt another uprising; angry political parties already have called mass demonstrations for later this month. The United States, which has more leverage over the Egyptian military than any other outside party, should use it to reverse what amounts to a coup.

The generals’ justification for their proposed decree will sound familiar to any student of the Mubarak regime: They claim to be protecting the country from Islamic fundamentalists, who appear likely to capture a plurality of seats in parliament. In fact some Egyptian secular parties unwisely encouraged the supra-constitutional articles in the hope they would guarantee civil liberties and a secular state. Yet while offering a nod in that direction, the proposed charter mainly serves to lock in the military’s overweening power, including control over a large part of the economy.

During eight months of interim rule, the Supreme Council of the Armed Forces has shown contempt for the freedoms it claims to be protecting. Some 12,000 civilians have been subjected to summary trials in military courts. On Sunday one of the heroes of the revolution, blogger Alaa Abdel Fattah, was summoned by a military prosecutor after he published an article detailing the military’s responsibility for violence against a march of Christians in Cairo last month. When Mr. Fattah refused to cooperate, he was jailed.

The Obama administration demonstrated during the revolution that it can sway Egypt’s generals: Washington successfully insisted that violence not be used to end the uprising and that Mubarak be forced to step down from the presidency. Now the administration — and Congress, if necessary — must insist that the armed forces respect their promise of a democratic transition. Egypt’s constituent assembly must have democratic legitimacy; Mr. Fattah and other political prisoners must be released. Above all, Egypt’s army should not be allowed to perpetuate its role as an unaccountable authority while still receiving billions in U.S. aid.