The U.S. State Department said there were mixed reports about events in Myanmar. The government there confirmed this week that military jets fired on rebel positions in northern Kachin, where fighting last year ended a 17-year peace.
"Our view is that all sides need to cease and desist and get into dialogue with each other, and we're making that point to both the government and to Kachin representatives," State Department spokeswoman Victoria Nuland said.
Myanmar, a country also known as Burma, has received praise for a series of political reforms that began with general elections in 2010. Recent security challenges and human rights concerns, however, have overshadowed some of the political gains.
Hugo Swire, a state minister for the British Foreign and Commonwealth Office, said London has deep concerns about the fighting between the Myanmar military and the rebel Kachin Independence Army.
"An escalation in hostilities would put at risk the chance of a lasting peace in Burma," he said in a statement. "It is imperative that military commanders in Burma heed their president's calls for an end to hostilities."