Peace Talks in Myanmar Jeopardized by Killing of Rebels BANGKOK - Ethnic minority groups in Myanmar said on Thursday that peace talks with the government, one of the cornerstones of the country's reform program, were in jeopardy after at least 23 rebel cadets were killed in an attack by the military. The shelling on Wednesday, which struck an officers" training facility near the Chinese border that is run by the rebel group, the Kachin Independence Army, was the most severe flare-up of violence since militants from the Kachin ethnic group and government troops battled around the rebel capital, Laiza, two years ago. The shelling, which rebel officers said killed men from a number of different ethnic groups who were training at the facility, cast doubt on the government's ability to bring about a nationwide cease-fire, a plan that has been repeatedly postponed in recent months after skirmishes. "This has caused a tremendous obstacle in building trust," the United Nationalities Federal Council, a coalition of ethnic groups, said in a statement on Thursday. The group said the military had "deliberately planned and fired" artillery at the Kachin facility and questioned the "genuine desire" of the military for peace. Photos of the rebels" corpses were widely circulated on the Internet. "We are outraged," said Mong Gwang, a captain with the Kachin Independence Army, which controls large swaths of territory along the border with China. This means further conflict is coming. The escalation of violence came just days after President Obama visited Myanmar and warned of backsliding in the country's transformation from dictatorship to democracy. Myanmar has been locked in an intermittent civil war from its earliest days of independence from Britain in 1948, and a cease-fire is considered a crucial part of President Thein Sein's stated desire to deliver it from its abject poverty and dictatorial past. U Hla Maung Shwe, a director of the Myanmar Peace Center, which is coordinating talks between the government and ethnic groups, sought to play down the shelling, calling it a response to a rebel attack. "The Tatmadaw shelled back," he said, using the formal name for the army. I think this is just an accident. The Kachin, who inhabit the resource-rich highlands in the foothills of the Himalayas, are among 16 ethnic groups negotiating with the government for a cease-fire. Negotiations have stumbled over the fundamental question of whether Myanmar will remain a united and highly centralized country controlled by the Burman ethnic group, or whether power will be devolved to minority groups. U Saw Than Myint, a representative of the Shan ethnic group, said talks faltered in September when the military pulled back from an offer to create a federal army. Mr. Saw Than Myint said he believed that Wednesday's attack was an effort to put pressure on the Kachin to agree to a cease-fire. "This is unacceptable, and it could backfire for the overall peace efforts," he said. Myanmar's military, which has a powerful and largely unchecked role in the nominally civilian government, has become increasingly assertive in recent months. Military officers in Parliament recently proposed that the National Defense and Security Council, a powerful and somewhat secretive body in which the military is heavily represented, be granted more power.