The top US military commander, Gen Martin Dempsey, says he is concerned about "the potential for civil unrest" as Europe's financial crisis unfolds.
Gen Dempsey said it was unclear the latest steps taken by EU leaders would be enough to hold the eurozone together, adding that a break-up could have consequences for the Pentagon.
Twenty-six of the 27 EU countries have agreed to forge a tighter fiscal union.
Only the UK refused to sign up to a new treaty, citing national interest.
Gen Dempsey, who is chairman of the Joint Chiefs of Staff, told an event hosted by the Atlantic Council, a Washington think-tank: "The eurozone is at great risk."
"I know that they've taken some measures here with the 17 members of the eurozone to try to better align... monetary and fiscal policy. But it's unclear, to me at least, that that will be the glue that actually holds it together." Full story/source