Officials say the US is reviewing its support to "ensure that it is contributing to a solution".
It follows the two leaders' heated clash at the White House last week.
UK Prime Minister Keir Starmer has reiterated he's prepared to send British troops to Ukraine to police a peace agreement with Russia.
But Matthew Savill, director of military sciences at defence thinktank RUSI, says we may never reach that point.
IN: 'There is…
DUR: ...ceasefire.'
OUT: 19 seconds
http://www.fsnradionews.com/feeds/0304ukraine-savill1.mp3