WASHINGTON (Reuters) - The United States on Friday urged supporters of the Syrian government to press it to  participate fully  in negotiations with the opposition, saying a lack of a political resolution in the war-torn country threatened indefinite instability. In a statement, a spokeswoman for the State Department said the United States wanted the government s supporters  to use their leverage to urge the regime to participate fully in tangible negotiations with the opposition in Geneva.   The United States urges all parties to work seriously toward a political resolution to this conflict or face continued isolation and instability indefinitely in Syria,  spokeswoman Heather Nauert said in a statement. A United Nations negotiator characterized a round of peace talks that ended on Thursday as a missed opportunity, and he laid most of the blame at the feet of Syria s government. 
U.S. says it wants Syrian government to negotiate 'seriously' with opposition