Trump had hoped to arrange a bilateral meeting between Putin and Zelenskiy, but that has also proven difficult.
Russian Foreign Minister Sergei Lavrov told NBC on Friday that there was no agenda in place for a sitdown with Zelenskiy.
Neither Ukraine's presidential office nor the defence ministry immediately responded to Reuters' request for a comment outside business hours.
The White House and the Pentagon also did not immediately respond to requests for comment.
(Reporting by Bipasha Dey in Bengaluru and Lidia Kelly in Melbourne; Writing by James Oliphant; Editing by Don Durfee and Diane Craft). »