Armed Mexican soldiers interrupted the burial of a Mexican-born U.S. Marine killed in Iraq and briefly detained at least a dozen Marines participating in the ceremony Sunday. U.S. Ambassador Tony Garza said he was "outraged" over the July 4 incident, which involved a dispute over two ceremonial, non-working rifles carried at the cemetery by a Marine color guard.

The incident occurred at the burial of Lance Cpl. Juan Lopez Rangel, 22, who was killed in an ambush in Ramadi on June 21. Lopez, a legal permanent resident of the United States who was granted citizenship posthumously, had moved to Georgia when he was 15 from his home town of San Luis de la Paz in central Guanajuato state, where his funeral and burial were held.

Lopez's family had requested that he be buried with full U.S. military honors, which normally include a 21-gun salute. But the Mexican Defense Ministry, citing the prohibition on foreign troops carrying weapons in Mexico, turned down a request for the Marines to carry guns for the salute, said Jim Dickmeyer, a spokesman for the U.S. Embassy in Mexico City.

The Iraq war is an emotional subject in Mexico, where President Vicente Fox and the vast majority of the public opposed the U.S.-led invasion. The Mexican media have reported that at least 17 Mexican-born U.S. troops have been killed in Iraq, along with at least 13 more born in the United States to Mexican parents.

While there has been great public sympathy for the dead soldiers -- including several thousand mourners who turned out Sunday -- the deaths have created even more resentment about the war.

The six pallbearers, all Marines from Lopez's unit who had flown in from Camp Pendleton in California, carried no weapons, Dickmeyer said. They were joined by a Marine color guard from the embassy made up of two flag-bearers accompanied by two Marines carrying only the ceremonial M-14 rifles, which do not fire ammunition, Dickmeyer said.

Problems began as the six pallbearers were folding the U.S. flag in preparation to hand it to Lopez's widow, said Dickmeyer, who was present. A Mexican Army captain, backed by at least 10 soldiers in combat uniforms and helmets, demanded to see documents giving the Marines permission to carry the guns in Mexico, he said.

Dickmeyer said he suggested the captain wait until the ceremony was over to discuss the matter. But the officer continued demanding to see documents and confiscate the guns, even as a U.S. Marine played taps on his bugle, Dickmeyer said.

When taps was finished, the color guard turned about-face and marched back to the three embassy vans in which they had arrived. They put the flags and guns in the vehicles. Mexican soldiers stood in front of the vehicles and would not permit them to leave, Dickmeyer said.

Photographs in Mexican newspapers Monday showed a Mexican soldier jabbing his finger toward the face of a Marine officer in an apparently heated discussion.

For at least 40 minutes, the Mexican captain and U.S. Embassy officials made phone calls to try to resolve the matter, Dickmeyer said. Finally, he said, the captain and his troops simply walked away, without explanation, and the Marines drove back to Mexico City.

"I am outraged that this would take away from the ceremony honoring U.S. Marine Juan Lopez Rangel, whose family requested that he be buried in his town of birth with full military honors," Garza said in a statement issued Sunday night.

The Mexican Defense Ministry had no comment Monday. Salvador Musalem, a spokesman for the Mexican Foreign Ministry, said Mexican Defense Minister Gerardo Vega Garcia and U.S. Defense Secretary Donald H. Rumsfeld were scheduled to discuss the matter by telephone Monday.

Lopez's cousin, Octavio Lopez Torres, said Monday that the Mexican soldiers had shown a "lack of respect."

"Maybe they were just doing their jobs, but they have to respect that it was a painful moment," Lopez said. "The family was just trying to get through the moment. They could have waited."