Trump’s fired military guru says he doubts the Republican nominee can broker peace between Ukraine and Russia

Donald Trump's former military guru has pooh-poohed the former president's campaign trail refrain that he could broker a peace deal between Ukraine and Russia "in one day" .

“I don’t really buy it,” said HR McMaster, who was appointed as a national security adviser by Trump in 2017 and was forced out in 2018, in an interview with CBS News anchor Robert Costa on ‘Face the Nation’ on Sunday.

"I think it's a real myth, a real misunderstanding of war, to assume that you can get a favourable political outcome without a favourable military outcome. That's never really happened in war.”

"And so I think the right course of action, if you want to accelerate progress toward a settlement, is to convince Putin that he's losing the war. I think that's the only way you get a favourable settlement.

"How do you do that? You demonstrate our resolve to continue to support the Ukrainians as they defend themselves against this continued onslaught by the Russians."

Donald Trump has repeatedly claimed that he could broker a peace between Russian president Vladimir Putin and Ukrainian president Volodymyr Zelensky before he is even inaugurated as president .

Meanwhile, Republican politicians have frequently tried to curtail US aid to Ukraine , sometimes calling for Ukraine to cede territory to its bellicose eastern neighbour to end the war of aggression.

McMaster, who is currently promoting a new book entitled At War With Ourselves about his time in the Trump White House, is a retired general and prolific military strategist who made his name with a widely-read critique of America's war aims in Vietnam.

Barely a year after his appointment to the White House, reports surfaced that Trump was planning to fire him , causing McMaster to voluntarily step one week later.