WASHINGTON (AP) – The top U.S. military commander in Europe said Tuesday that several NATO countries are working on contingency plans for possible military action to end the two-year civil war in Syria as President Bashar Assad’s regime accused U.S.-backed Syrian rebels of using chemical weapons.

The Obama administration rejected the Assad claim as a sign of desperation by a besieged government intent on drawing attention from its war atrocities – some 70,000 dead, more than 1 million refugees and 2.5 million people internally displaced.

While a U.S. official said there was no evidence that either Assad forces or the opposition had used chemical weapons in an attack in northern Syria, the chairman of the House Intelligence Committee, Rep. Mike Rogers, R-Mich., said there was a “high probability” that the government had used the weapons.