US President Donald Trump said he rejected a Pentagon proposal to cut military healthcare by $2.2 billion, although such a reduction did not appear to have been formally proposed.

Politico reported on Sunday that Pentagon officials had proposed slashing military healthcare by $2.2 billion.

However, US Defense Secretary Mark Esper said on Monday that he had not directed or approved any cuts to the military healthcare system in future budgets.

Trump said in a tweet late on Monday: "A proposal by Pentagon officials to slash Military Healthcare by $2.2 billion dollars has been firmly and totally rejected by me."

His tweet suggested that the proposal had made it to the White House. However, sources told Reuters the proposal was never formally presented to Pentagon leadership or the White House.

Tweets by Trump and his political rival Joe Biden, who also voiced opposition to cuts, reflect an eagerness to show solidarity with the United States military ahead of the November presidential election.