(QHA) -

Washington has accused Moscow of cynically exploiting an internationally backed cease-fire deal for eastern Ukraine by supporting a fierce assault by pro-Russian separatists who seized the strategic town of Debaltseve.

The White House said on February 18 that Russia has failed to live up to terms of a new cease-fire deal reached in Minsk and is "at risk of greater costs," such as further sanctions.

The U.S. State Department said it did not consider the cease-fire "dead," but expressed concern about ongoing violence.

U.S. Secretary of State John Kerry on February 18 urged Russian Foreign Minister Sergei Lavrov to stop attacks by Russian troops and separatist fighters against Ukrainian government troops.

The statements follow the withdrawal of hundreds of exhausted government troops from Debaltseve, a strategic railway hub between the main separatist-controlled cities of Donetsk and Luhansk.

Separatist fighters on February 18 claimed total control of Debaltseve after Ukrainian President Petro Poroshenko confirmed what he called "a planned and organized withdrawal."

Defense officials in Kyiv said a total of 2,459 Ukrainian soldiers left Debaltseve on February 18.