moscow u.s. tip-off plan attack st. petersburg help save many live russia unite state try cooperate way future kremlin spokesman dmitry peskov say monday washington provide intelligence russia help thwart potentially deadly bomb u.s. russian officials say sunday rare public show cooperation despite deep strain two countries call anything ideal example cooperation fight terrorism peskov tell reporters conference call aim standards tip-off result detention seven allege supporters islamic state militant group st. petersburg last week peskov say russia federal security service say friday plan attack public place dec. 16 weapons explosives find suspect search peskov say russian american security service contact first time cooperation efficient meaningful information help save many live spokesman tell reporters ask president vladimir putin u.s. president donald trump putin discuss possible meet peskov reply issue bring yet kremlin say u.s. tip-off plan attack 'saved many live