ASTANA (Reuters) - Syrian groups who choose to boycott the Russia-sponsored national congress next month risk being sidelined as the political process moves ahead, Russian negotiator Alexander Lavrentyev said on Tuesday. Lavrentyev said the most important task of the congress was launching a constitutional reform.  Lavrentyev spoke to reporters after talks with Turkish and Iranian delegations, as well as Syrian government and rebel groups, in Kazakhstan which he said failed to produce finalised prisoner swap documents. 
Those who boycott Syrian congress may be sidelined, Russia warns