WASHINGTON - The Pentagon has extended the tour of 2,200 Marines in Afghanistan, after insisting for months that the unit would come home on time.

The Camp Lejeune, N.C.-based 24th Marine Expeditionary Unit, which is conducting combat operations in the volatile south, will stay an extra 30 days and come home in early November rather than October, Marine Col. David Lapan confirmed Thursday.

Military leaders as recently as Wednesday stressed the need for additional troops in Afghanistan. Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, has often praised the work of the 24th MEU in fighting Taliban militants in Helmand province.

Defense Secretary Robert Gates, however, has repeatedly said he did not intend to extend or replace the U.S. Marines in Afghanistan, calling their deployment there an extraordinary, one-time effort to help tamp down the increasing violence in the south.

Asked about the possibility of an extension in early May, Gates said he would "be loath to do that." He added that "no one has suggested even the possibility of extending that rotation."

Pentagon press secretary Geoff Morrell said the longer tour does not open the door to an extension beyond the 30 days, nor to the possibility of replacing the Marines with other U.S. troops when they come out in November. "This is a slight addition to this tour and nothing more," he said.

He added that commanders in Afghanistan "asked for 30 more days to milk the fighting season to the bitter end and cement the gains they have made in the south."

Commanders faced with increasing violence have said they need at least 7,500 more troops in Afghanistan. And President Bush and defense officials have said they hope to identify additional units by the end of the year that could go to Afghanistan early next year.