As promised in July, the Department of Homeland Security said it had revamped the program to focus on rooting out undocumented immigrants who have committed serious crimes.

The changes also require law enforcement officers enrolled in the program to abide by federal anti-discrimination law. In addition, federal officials pledged to supervise the program more closely, flag problems and field complaints from the public.

Civil libertarians and immigration advocacy groups had complained participating police agencies had unduly made targets of immigrants who commit relatively minor offenses, like traffic violators. There have also been widespread accusations police officers have engaged in racial profiling. Much of the criticism has been focused here in metropolitan Phoenix, where the Maricopa County sheriff has made a national name for himself with his immigration crackdown.

Some critics, including most recently several Hispanic members of Congress, had urged the Obama administration to drop the program because of the problems, and those opponents were little mollified by the revisions announced Friday.

But Immigration and Customs Enforcement officials, suggesting the changes would address the troubles, said they intended to expand the program, known as 287(g) for the section of the 1996 law that authorized it.

Officials said ICE had renewed agreements with 55 state and local law enforcement agencies. An additional 12, officials said, have reached tentative agreements that, if confirmed by their local governing bodies, will increase participation in the program to 67 agencies, from the current 66. ICE also remains in negotiations with six other agencies, including one of the largest, the Los Angeles County Sheriff’s Department.

Six previously participating agencies, however, have withdrawn, including the Houston Police Department. Houston officials said they were wary of police officers’ acting as immigration agents and planned to enroll soon in a separate federal program that would allow all jail inmates, not just those suspected of being in the country illegally, to be screened for federal offenses, including immigration violations.

Nowhere has the 287(g) program been more controversial than in Maricopa County, where Sheriff Joe Arpaio, whose department has the largest number of personnel trained in the program, faces a Justice Department investigation over complaints of civil rights violations.

Lawsuits accuse deputies of singling out Hispanics for stops that include a check of their immigration status.

ICE announced Friday it had withdrawn its authorization for the sheriff’s street enforcement of immigration law, in which 100 federally trained deputies had been engaged. But, to the ire of immigrant advocates, the federal agency will continue to allow 60 deputies to screen jail inmates, who have accounted for a vast majority of the immigration arrests.

Mr. Arpaio has denounced federal officials for the changes and conducted a crime sweep Friday in Surprise, a Phoenix suburb, as a retort, saying he could pursue undocumented immigrants under state laws that bar activity like human smuggling.

“The sheriff is prone to rhetoric on occasion, and some of that is about ICE,” said John T. Morton, the agency’s director. “But I call things on the merits.”

The new agreements are the latest evolution of the program, which got under way in 1996 but did not begin to grow in earnest until after the Sept. 11 attacks. The immigration agency is requesting $68.1 million to run the program in the fiscal year that began Oct. 1.

More than 133,000 undocumented immigrants have been arrested through the program since January 2006, though ICE officials said they could not readily provide information on how many had been deported.

While opponents denounce the program as ineffective and prone to abuse, its defenders say there is no reason why undocumented immigrants who have committed a crime, even if not of the most serious nature, should be allowed to remain in the United States.

“Claims that the program was supposed to focus only on serious crimes are false,” said a joint statement by Representatives Trent Franks, a Republican whose district includes Maricopa County, and Lamar Smith, a Texas Republican who was an author of the 287(g) legislation. “In fact, the program was created to let state and local law enforcement officials help enforce all immigration laws, not a select few.”

The debate continued to boil here on Friday, when protesters marched on Mr. Arpaio’s downtown office, as they regularly do, around the time his crime sweep got under way 20 miles away in Surprise.

Later, at an outdoor news conference in Surprise, Mr. Arpaio said eight people suspected of being undocumented immigrants had been arrested under a state statute that forbids human smuggling.

“We will continue to do what we have been doing,” he said, fighting to speak over the din of shouting protesters.