US President Donald Trump and Russian counterpart Vladimir Putin discussed steps to ease Syria's civil war, in what the White House described as a "very good call" Tuesday.

"President Trump and President Putin agreed that the suffering in Syria has gone on for far too long and that all parties must do all they can to end the violence," the White House said after the two men spoke.

"The conversation was a very good one, and included the discussion of safe, or de-escalation, zones to achieve lasting peace for humanitarian and many other reasons."