About a dozen American troops from U.S. European Command on Tuesday arrived in Ukraine to help recover remains and investigate the downing of the Malaysian airliner that killed all 298 passengers aboard, officials said.
The State Department requested the team to "assess, advise, and provide recommendations to the U.S. Embassy" about support for the recovery operation, Navy Rear Adm. John Kirby, the Pentagon press secretary, said at a briefing with reporters.
Kirby said that the troops will not go to the crash scene in eastern Ukraine near fighting between the forces of the central government in Kiev and separatists backed by Russia.
"They will not leave Kiev," Kirby said of the U.S. troops who specialize in recoveries and analysis at crash sites. "Recovery operations are something, tragically and unfortunately, the U.S. military has to do and has to be good at."
The U.S. and NATO have charged that Malaysian Airlines Flight MH17 was brought down last month by a Russian surface-to-air missile system fired from an area controlled by the separatists.
The arrival of the team came as Russia continued its military buildup along the border and stepped up the pace of its training exercises, Pentagon and NATO officials said.
In Kiev, Ukraine government security officials said Monday they were preparing for a "massive assault" on the eastern city of Donetsk, the major separatist stronghold, state media reported.
Air Force Gen. Philip Breedlove, head of the European Command and Supreme Commander of NATO, met on the sidelines of a World War I commemoration in Belgium with NATO Secretary General Anders Fogh Rasmussen and British Prime Minister David Cameron to discuss the crisis in Ukraine.
"We are at a crucial point in history," Rasmussen said. "As we remember the devastation of World War I, our peace and security are once again being tested, now by Russia's aggression against Ukraine. And the criminal downing of Flight MH17 has made clear that a conflict in one part of Europe can have tragic consequences around the world."
NATO officials said that Russia now has about 20,000 troops massed on the border of Ukraine. At the Pentagon, Kirby would not put a figure on the buildup but said it was "north of 10,000. They are very capable and very ready," he said.