WASHINGTON (Reuters) - U.S. peace groups pledged on Sunday to start the new year with protests and vigils to mark the death of the 3,000th U.S. soldier in Iraq and to press their call for an end to the war.

"We must bear witness to this tragic milestone, even though many people are already beginning their celebrations of the new year," the group United for Peace and Justice said on its Web site.

A soldier killed by a roadside bomb in Baghdad on Saturday became the 3,000th American to die in Iraq since the U.S.-led invasion in 2003, according to the Web site www.icasualties.org.

A group of U.S. veterans that sets up crosses on a Santa Monica, California, beach every Sunday to remember American soldiers killed in Iraq added candles to mark the 3,000 milestone.

"We decided to do a special candlelight vigil tonight, partially because it"s New Year"s Eve but also because we don"t want people to forget the cost of this war," said Chuck Nixon, of the group Veterans for Peace. "Three thousand families have lost a son or daughter.

"Sometimes, people call this a protest. We don"t believe it"s a protest. We believe it"s a memorial honoring these soldiers."

United for Peace and Justice, a coalition of more than 1,300 U.S. peace groups, urged demonstrators to wear black armbands or ribbons with the number 3,000 in white print and to phone radio stations and write letters to newspapers to call attention to the death toll.

The American Friends Service Committee put out a call for anti-war activists to rally across the country on New Year"s Day to mourn American and Iraqi casualties in the war. Group members in Dallas planned to ring a bell to mark the deaths in their demonstration in front of City Hall.

"We"re not pretending to appropriately honor those who have died," said organizer Bill Betzen. "It"s just impossible."

In Pittsburgh, peace activists were to gather at a military recruitment center on Monday to mark the 3,000 milestone.

"These occasions can be important and take on tangible meaning if they provide a chance for personal reflection or spur people to take action that alters the future," the Pittsburgh Organizing Group said on its Web site.

Another candlelight vigil was set for Tuesday near Philadelphia"s City Hall with participants planning to read names of both U.S. military personnel and Iraqis killed.

Gold Star Families for Peace, an organization founded by prominent anti-war activist Cindy Sheehan after her son was killed in Iraq, is planning a rally in Washington on January 3-4 to press for immediate withdrawal from Iraq, as well as the impeachment of President George W. Bush.

United for Peace and Justice will stage a march in Washington on January 27 and urged supporters to arrange meetings with members of the new Congress on January 29 so they can lobby for an end to the war.

(Additional reporting by Joanne Allen)