Egypt's embattled military rulers faced pressure on all sides Thursday, with the newly empowered Muslim Brotherhood demanding the regime cede power as an intensifying standoff over American nonprofit employees imperiled U.S-Egyptian relations.

Coming nearly a year after a popular uprising toppled President Hosni Mubarak, the swelling tide of criticisms reflected a sense that the ruling Supreme Council of the Armed Forces is perpetuating many of the authoritarian abuses of the Mubarak era. The army has continued to violently supress protests, and many accuse the ruling generals of seeking to enshrine permanents powers for themselves.

The Muslim Brotherhood, a formerly outlawed group that has become the Supreme Council of the Armed Force's main opposition since dominating parliamentary elections, demanded on Thursday that the military allow Parliament to dissolve the current cabinet and form a new government. The military had tried to placate its critics by moving presidential elections to June, but the government's apparent inability to contain a deadly soccer riot last week has galvanized public anger.

We must start the formation of a coalition government immediately, to deal in particular with the economic situation and the state of lawlessness in this homeland, Khairat el Shater, deputy to the Brotherhood's Supreme Guide, said in an online statement. He faulted the government's mishandling of protests that have roiled Egypt.

Dealing with the demonstrators violently is a mistake, a sign of weakness and mismanagement by the Ministry of Interior, he said.

The United States has also become more vocal in its warnings to the military rulers. The United States and Egypt have for years enjoyed a mutually beneficial relationship, with America sending Egypt billions in military aid in exchange for Egypt upholding a peace treaty with Israel.

But that alliance has begun to fray as the government has pressed on with criminal charges against American citizens working for pro-democracy groups. The Senate had already conditioned this year's aid package on the Egyptian government pursuing democratic reforms, and the trial has raised the likelihood of the United States suspending aid.

Congressional support for Egypt -- including continued financial assistance -- is in jeopardy, Sen. McCain (R-AZ) said in a joint statement with Senator Kelly Ayotte (R-NH) and Senator Joseph Lieberman (I-CT), all of whom are preparing to travel to Egypt. A rupture in relations would be disastrous, and the risks of such an outcome have rarely been greater.

Egypt's rulers have remained defiant, with Prime Minister Kamal al-Ganzouri saying that Egypt will not back down because of aid or other reasons.