President Obama has said the new government is on a “dangerous path” marked by “arbitrary arrests, a broad crackdown on Mr. Morsi’s associations and supporters” and “violence that’s taken the lives of hundreds of people and wounded thousands more.”

Warning that “our traditional cooperation cannot continue as usual when civilians are being killed in the streets and rights are being rolled back,” the president canceled a planned joint military exercise. He pledged a review of the $1.3 billion a year in military aid to Egypt, and the State Department took steps to hold back some of the roughly $200 million in nonmilitary aid. But mindful of Egypt’s importance in the region, he stopped short of declaring the takeover an illegal “coup” or cutting off the aid, instead urging an early return to democracy.

Officials of the new government insist they are committed to establishing the rule of law, as soon as they overcome what they describe as the mortal threat to Egypt of violence by the Brotherhood and other Islamist supporters of Mr. Morsi.

The police appear to be rounding up Brotherhood members on the basis of their affiliation, without other publicly known evidence of crimes. Mr. Morsi is being held incommunicado at an undisclosed location. But government spokesmen insist that every individual, including Mr. Morsi, will be tried by a court and released if acquitted.

“It is up to the courts,” Nabil Fahmy, the interim foreign minister, said in a recent interview. All will be handled “in accordance with the rule of law,” he said.

But some of the recent charges, like those against the two Canadians, strain credibility. Tarek Loubani, a Canadian physician with Palestinian roots and a history as a liberal and pro-Palestinian activist, was in Egypt on his way to the Gaza Strip to provide training to Palestinian doctors. John Greyson, a liberal Toronto filmmaker whose work often focuses on cosmopolitan sexual themes, was with him, documenting the trip for a possible movie. A lawyer for the two said they were stopped at a checkpoint near a street battle, trying to walk back to their hotel after the 7 p.m. curfew.

“They were just in the wrong place at very much the wrong time,” the lawyer, Khaled El-Shalakany, said Saturday.