white house. reporter: president biden preparing for talks with vladimir putin in the hope of deterring russia from invading y ukraine. the president on imposing economic sanctions on russia as new intelligence estimates moscow could invade ukraine as soon as next month. this is the moment for russia to pull back their military buildup at the border. that diplomacy is the right path forward here. reporter: the russian president is expected to issue an ultimatum of his own. a written guarantee for biden to oppose nato and weapons systems from the military alliance for expanding into ukraine. putin called this a red line and an urgent threat to russian sovereignty. the meeting between biden and putin comes at a low point in relations between the two countries. it s their first conversation since july following their face to face summit in geneva. i came what i did do do. reporter: since then tensions