MOSCOW TO HOST SLAV CONGRESS, JUNE MOSCOW, March 6. /From RIA Novosti's Arina Dovgan/. Russian, Ukrainian and Belarussian Slavs are gathering for congress in Moscow, June 1-2--a date appointed today by the organising committee. Leading it is Speaker Gennadi Seleznev of the State Duma, Russia's lower parliamentary house. Prominent among congress goals is to rally the public for support of the Russo-Belarussian union, says Mr. Seleznev. The collapse of the Soviet Union led to a hasty coercive division of a Slav unity which had taken shape over centuries, point out the congress organisers. The International Foundation for Slavonic Culture and Writing, the Russian Orthodox Church and the Moscow mayoral office are prominent among them.