Washington calls on Serbia to withdraw its military forces from the border with Kosovo.
National Security Council spokesman John Kirby said the United States is monitoring a large Serbian military buildup along the border with Kosovo, including advanced artillery, tanks and mechanized military units.
"This is a very destabilizing development that has happened over the last week," he said.
He said that the United States is seeing that the disturbing cycle of violence in Kosovo has worsened.
"Recently, the most disturbing incident was the one that happened a few days ago on September 24. That attack was well coordinated and planned," he said.
"The types of weapons that were found pose a threat not only to Kosovo personnel, but also to international personnel, including NATO troops," stated Mr. Kirby.
The White House National Security Adviser said NATO is increasing its peacekeeping forces in Kosovo because of the disturbing cycle of violence there.