CAIRO, Egypt — Egypt’s parliament yesterday approved a controversial set of amendments to the constitution that the opposition has denounced as a blow to democracy in this top American ally in the Middle East.

President Mubarak has billed the changes as part of a reform plan to increase democracy in the country that he has ruled unchallenged for a quarter of a century.

But the opposition has said the changes will restrict judicial supervision of elections that they call vital to preventing vote fraud. The amendments also write permanently into the constitution strong security powers for the president that they fear will be abused.

The changes come at a time that America has reduced public pressure on Egypt to bring greater democracy. Two years ago, the Bush administration made reform in Egypt a top priority, but more recently, it has spoken out less often, more concerned with winning Cairo’s support in Middle East crises, such as the situation in Iraq.

The 454-seat parliament voted on the measures a day earlier than expected after hours of discussion. “With our blood and souls, we sacrifice ourselves for you, Mubarak,” the ruling party lawmakers chanted before the results of the vote were announced.

The 34 amendments passed with a vote of 315 in favor, parliament speaker Fathi Sorour said on Egyptian television. The amendments will now be put before a popular referendum, expected in late March or early April.

Mr. Sorour did not announce the “no” votes in the session. But the head of the opposition Muslim Brotherhood’s bloc in parliament, Mohammed Saad al-Katatni, said 108 opposition lawmakers and two members of the ruling National Democratic Party voted against the amendments. The opposition, led by the Brotherhood, had boycotted debate over the measures Sunday to protest the changes, but at the last minute decided to cast votes to get their rejection on the record, Mr. Katatni told the AP.