A Florida National Guardsman who abandoned his unit after returning from Iraq in October surrendered to military officials Monday afternoon, claiming conscientious objector status.

Army Staff Sgt. Camilo Mejia, 28, of Miami is believed to be the first soldier to turn himself in after refusing to return to Iraq, his lawyer said.

"I am saying no to war; I have chosen peace," Mejia said at a morning news conference at the Peace Abbey, a pacifist institute, in nearby Sherborn, Mass. "I went to Iraq and was an instrument of violence, and now I have decided to become an instrument of peace."

Coinciding with the first anniversary week of the start of the war in Iraq, Mejia's surrender will be a "test case for the military that will have broad impact on other objectors or potential objectors," said Tod Ensign of Citizen Soldier, which he described as a soldiers' rights advocacy organization.

Ensign said that as many as 600 soldiers have failed to return to their units after home leaves from Iraq.

Mejia, who was born in Nicaragua and is a permanent U.S. resident but not a citizen, arrived in Iraq with his infantry battalion in May 2003 after a brief stint in Jordan. He returned to the United States in late September to address immigration issues.

During his time in Iraq, he said, he became increasingly convinced that war was unjust, citing a firefight after an ambush on his unit that left several civilians dead. He decided not to return to his unit for redeployment on Oct. 16.

"I am glad to hear that he turned himself in. His unit had tried to get in touch with him when he was gone and could not reach him," said Lt. Col. Ron E. Tittle, chief of public affairs for the Florida National Guard, who said that any legal issues probably would be dealt with at Fort Stewart, Ga., where Mejia's unit was assigned after it was activated in January 2003. "We wish he could have returned and served with his comrades and served over there," Tittle said. "But that is another issue."

In a story published in Monday's Chicago Tribune, some of Mejia's commanders suggested that he was an unmotivated soldier who had lost his nerve.

Mejia disputed claims that he had not performed well under fire. "I was there and did my job as a soldier," he said.

After signing documentation saying he was a conscientious objector and speaking with reporters for about a half-hour Monday, Mejia boarded a school bus along with his parents and other family members and about two dozen peace activists to this air base on the western outskirts of Boston.

Wearing a medallion that read "Make me an instrument of your peace" and carrying a backpack containing a Bible, clothes and writing tools, Mejia surrendered to two military policemen. He was released on his own recognizance and ordered to report to his battalion's Miami headquarters, said Louis Font, his attorney.

Along with his mother and aunt, Mejia boarded a flight to Fort Lauderdale late Monday evening, said Font, a West Point graduate and conscientious objector from the Vietnam War, who specializes in military law.

At the news conference, held outdoors in front of a stone memorial for unknown civilians killed in war, Mejia said he had spent the past five months hiding out with friends and relatives, mostly in New York City. He chose to surrender in Massachusetts, he said, after a visit earlier this year to the Peace Abbey, which also houses a small museum with artifacts from Mohandas K. Gandhi, the Dalai Lama, Mother Teresa and other pacifists. "I have not committed a crime and I should not run," he said.

Font said that if Mejia is court-martialed, he could face maximum penalties of five years in a military prison for desertion and an additional five years for missing a movement to avoid a hazardous duty, followed by a dishonorable discharge.

The desertion charge would require prosecutors to demonstrate that Mejia did not intend to return to duty, which his surrender shows is not true, Font said, adding that he will argue that Mejia's case should be handled administratively, without a trial. To be classified as a conscientious objector Mejia would have to demonstrate that he is opposed to all war, "and he certainly is that," Font said.

Mejia's mother, Maritza Castillo of Miami, said she is scared of what might happen to her son but hopes he will be treated fairly. "I am proud of him. I want justice," she said.

Camilo Mejia of Miami is surrounded by supporters, including Fernando Suarez del Solar of San Diego, left, whose Marine son was killed in Iraq, after a news conference in Sherborn, Mass.