CAIRO — Egypt’s new military-led government enlisted internationally recognized figures to serve as its public face and promised swift elections on Tuesday, but introduced a transitional plan that was widely criticized as muddled, authoritarian and rushed.

The so-called road map, in the form of a “constitutional declaration” by the military-appointed president, elicited immediate opposition from civilian leaders across the political spectrum, including the liberals and activists who sought the ouster of President Mohamed Morsi, the faction of ultraconservative Islamists who joined them and the many thousands protesting to demand his reinstatement.

The declaration, however, made clear that the government drew its authority only from the military commander who executed the takeover, Gen. Abdul-Fattah el-Sisi. The interim president, Adli Mansour, a senior judge, cited the general’s brief statement as the basis of his own authority, and in confirmation the general’s words were printed as law in the official Gazette.

“It is now officially a coup,” Nathan Brown, a political scientist specializing in Egyptian law at George Washington University, wrote in assessing the text.

The military-led government widened its crackdown on Mr. Morsi’s Islamist supporters a day after security forces shot hundreds of them and killed more than 50 at a sit-in to demand his reinstatement. Security officials blamed the Islamists for instigating the lopsided clashes, and as part of its investigation of the episode ordered the arrests of 650 leaders of the Muslim Brotherhood, Egypt’s mainstream Islamist movement, and of Gamaa Islamiyya, a more conservative and once-violent group.

The officials said they had also arrested more of the former president’s top advisers. Brotherhood officials said they had lost contact with about 250 members of their leadership, in addition to the dozens — including Mr. Morsi — known to be detained.

At the same time, Egypt received a crucial financial lifeline from two oil-rich Arab monarchies that have made no secret of their fears of both Arab Spring democracy movements and the Muslim Brotherhood. The United Arab Emirates said it would provide a grant of $1 billion and an interest-free loan of $2 billion, while Saudi Arabia was reportedly working on providing an additional $5 billion. The donations are needed urgently because the turmoil surrounding Mr. Morsi’s overthrow has pushed the teetering Egyptian economy closer to the brink of collapse.

The new appointments, including a liberal economist as prime minister and the diplomat Mohamed ElBaradei as a vice president for foreign relations, appeared intended to reassure the Western allies and donors Egypt must depend on.

The new prime minister, Hazem el-Beblawi, is a prominent economist who served as finance minister under an earlier interim government. A founding member of the Social Democratic Party, he has criticized former President Hosni Mubarak and Mr. Morsi as failing to move fast enough to open up the economy, reform Egypt’s bloated and unaffordable subsidy programs and provide for the poor.

Mr. Beblawi is ideally suited to negotiate with the International Monetary Fund over a package of changes tied to a pending $4.8 billion loan, a deal that seemed out of reach after Mr. Morsi’s ouster but is still considered essential to save the economy. With a Ph.D. from the Sorbonne, Mr. Beblawi has written three books on Middle East economics, worked as a senior official of the United Nations and advised the Arab Monetary Fund. He resigned after four months as finance minister under the previous military-led transitional government — after Mr. Mubarak’s ouster — after soldiers shot dozens of mostly Coptic Christian demonstrators and the generals blamed them for scaring their troops.

Before the current crackdown, Mr. Beblawi had also welcomed the overthrow of Mr. Mubarak as providing an opportunity for Islamists to enter the democratic process. “The positive thing that resulted from this was that it gave a chance for the Muslim Brotherhood and political Islam, which have always been persecuted and wrongfully treated for a long time,” he said in an interview published last month in an English language-newspaper here.

Mr. ElBaradei, who won a Nobel Prize for his work with the United Nations’ nuclear watchdog, was the new government’s first choice for prime minister. But his appointment was opposed by the ultraconservative Islamist Al Nour party, which had agreed to back Mr. Morsi’s ouster. After Mr. ElBaradei’s rejection — while he was on his way to his swearing-in, the Islamist party’s leader said — the government cycled through two other candidates before persuading Mr. Beblawi to take the job.

The new “constitutional declaration” laid out an election schedule that analysts called implausibly speedy. The plan calls for a panel of 10 jurists — 6 judges and 4 law professors — to present a sweeping package of amendments in just one month. A group of 50 representatives of various government institutions, parties, guilds and social groups — including 10 who are either women or young — will then review the text for two months. But it is not clear what power they have to make changes or how they will make their decisions. A national referendum on the charter is set for a month after that, with parliamentary elections within the next month.