WASHINGTON - Secretary of State John Kerry is warning Russia of harsher economic sanctions if it does not back down from involvement in Ukraine.

Kerry was testifying Tuesday before a Senate panel. He said pro-Russia demonstrations at regional government headquarters in Kharkiv and the Donetsk regional administration were contrived and a pretext for military intervention.

Kerry said the U.S. and European allies were united and willing to impose tough new penalties on Russian energy, banking and mining if Moscow fails to honor a sovereign Ukraine.

Kerry said he would meet next week in Europe with Russia Foreign Minister Sergey Lavrov and Ukrainian officials. He said Russia has a choice and can work with the international community.

Russia annexed Crimea last month. (AP)