Egypt announced the ratification of a new Islamist-backed constitution Tuesday, a move that many here hope will end weeks of bitter political turmoil.

Nearly 64 percent of the 17 million Egyptians who voted in a national referendum this month approved the document, Egypt’s electoral commission said.

The charter’s adoption signifies a victory for Egypt’s elected president, Mohamed Morsi, and his Islamist backers, after months of political conflict that saw the Islamists square off against a broad but disparate opposition composed of liberals, secularists and old regime loyalists. Protests from both sides, over the balance of power in Egypt and the religious character of its guiding charter, occasionally led to violence.

The United States, Egypt’s primary benefactor, reacted to the news cautiously, saying “democracy requires much more than simple majority rule. It requires protecting the rights and building the institutions that make democracy meaningful and durable.”

In a statement, the U.S. government urged those who opposed the charter to continue engaging in the political process, and reminded those who supported it to “engage in good faith.” Both sides, the State Department said, should “recommit themselves to condemn and prevent violence.”

Critics of the charter say it will deepen the influence of Islamic law while failing to protect rights of women and minority groups.

Opposition leaders, who mounted a last-minute campaign for a “no” vote in the referendum, said over the weekend that their failure to defeat the document still yielded some positive points. The high number of “no” votes — about 36 percent — signifies an important show of force as the country hurtles toward a new round of elections in two months, they said.

Under the new charter, the government must hold elections for the lower house of Parliament within 60 days. Opposition groups said they are likely to compete in the elections, while continuing the push to annul the constitution.

“We can say that we are diversifying our options, using all possible means to say that Egypt is not up for this kind of extortion,” said Hussein Abdelghani, spokesman for the opposition’s main alliance, the National Salvation Front.

The new constitution officially replaces the country’s 1971 charter, which was written under the military regime of Anwar Sadat and remained in place until the aftermath of the popular uprising that ousted Sadat’s successor, Hosni Mubarak, in February 2011.

Regardless of the constitution’s approval, Abdelghani said that politics in Egypt would be different in the months ahead.

“Now there is a balance in political life. This is what changed in the last month and a half,” he said. “The [opposition] now has a title, and there is a force now to contend with the Islamists.”

In its statement, the State Department said that “only Egyptians” can decide their political future.

. . . Egypt needs a strong, inclusive government to meet its many challenges,” the U.S. government said. “Its future depends not on the ability of one side to prevail over the other, but on the commitment of all to engage in an inclusive process to negotiate their differences . . . and to find a more united path forward.”