It's unfortunate the Russian Co-Chair did not accept the invitation. US Department

The US Department of State's Bureau of European and Eurasian Affairs writes on his twitter page. ''The U.S. OSCE Minsk Group Co-Chair spoke with her counterparts today to discuss the future of Nagorno-Karabakh. It's unfortunate the Russian Co-Chair did not accept the invitation. We look forward to the Minsk Group’s continuing work''.