says the possibility of ukraine joining nato is a threat to russia. eva, what do we expect of this call between biden and the ukrainian president? reporter: this call is aimed to keep president zelensky in the loop. president biden expected to update him on the strategy of engaging with russia. of paramount concern is for the u.s. to emerge from this entire negotiation and episode with a diplomatic solution, without russia invading ukraine. now, in terms of what russia wants, russia wants legally binding skurpt guarantees. they want no membership for ukraine in nato and a rollback of military deployments in eastern urine. congressman adam schiff who chairs the intelligence committee, he was asked about this today, and he is very concerned about this. he believes the threats from vladimir putin are not hollow