taormina italy ask report donald trump son-in-law try set secret channel communication russia president take office u.s. national security adviser h.r mcmaster say so-called back-channeling normal mcmaster decline speak specifically case jar kushner serve senior adviser trump ask would concern someone administration try set back channel russian embassy kremlin reply back-channel communications number individual countries generally speak back-channel communications allow communicate discreet manner mcmaster say pre-expose sort content kind conversation anything concern it reuters report last week proposal back channel discuss mcmaster predecessor mike flynn russian ambassador trump prepare take office washington post report friday kushner participate conversation mcmaster say 'not concern kushner back-channel report