US President Donald Trump is facing a backlash over reports he mocked American soldiers killed in action as "losers" and "suckers".

The alleged remarks were first reported in the Atlantic magazine, and some details were corroborated by the Associated Press and Fox News.

But the president and his allies have denied he made the remarks.

Veterans' groups were among those who attacked the president over the reports.

Progressive group VoteVets posted a video of families whose children were killed in action. "You don't know what it is to sacrifice," says one.

Paul Rieckhoff of the Iraq & Afghanistan Veterans of America, tweeted: "Who is really surprised by this?"

Analysts say the comments could prove damaging with the president needing support from military voters as he bids for re-election.