Donald Trump has fired off on Twitter after footage emerged of the US President struggling to walk down a ramp, igniting mockery on social media and speculation about his health.

Videos showed Trump walking unsteadily down a ramp after giving a speech to the graduating class at the United States Military Academy in West Point, New York – which he blamed on a "slippery" ramp.

"The ramp that I descended after my West Point Commencement speech was very long & steep, had no handrail and, most importantly, was very slippery," the 74-year-old tweeted.

"The last thing I was going to do is 'fall' for the Fake News to have fun with. Final ten feet I ran down to level ground. Momentum!"

Vox journalist Aaron Rupar poked holes in the President's indignant defence, saying it was "worth noting that it was sunny throughout Trump's appearance at West Point. If the ramp was indeed 'slippery' it wasn't because of rain. And it certainly didn't appear to be steep".

Rupar also pointed out the leader "repeatedly" having trouble pronouncing the name of General Douglas MacArthur; while other videos showed him struggling to lift a glass of water to his mouth.

The ramp that I descended after my West Point Commencement speech was very long & steep, had no handrail and, most importantly, was very slippery. The last thing I was going to do is “fall” for the Fake News to have fun with. Final ten feet I ran down to level ground. Momentum!

— Donald J. Trump (@realDonaldTrump) June 14, 2020

While the White House released the results of the President's annual physical check-up earlier this month, concluding that he "remains healthy", the incidents provoked mockery and speculation about his state on Twitter, with the hashtags #TRUMPstroke and #TrumpIsNotWell trending in the US.

While he praised the "righteous glory of the American warrior", Mr Trump largely sidestepped the recent controversies over racial unrest and the military's role in putting it down.

"America is the greatest country in human history," he told the 1107 newly-minted second lieutenants.

But he made no direct mention of the recent racial turmoil, barely mentioning recent dissent from top military figures over his threat to employ active duty troops to put down demonstrations, stemming from the death of George Floyd.

Trump's closest mention of recent events came when he said, "I also want to thank the men and women of our National Guard" for responding to "challenges from hurricanes and natural disasters to ensuring peace, safety and the constitutional rule of law on our streets".

"McGarther" -- Trump also repeatedly had trouble with General Douglas MacArthur's name pic.twitter.com/HLSwbol2yL

— Aaron Rupar (@atrupar) June 13, 2020

The President also referred only passingly to the nation's racial challenges.

"The army was at the forefront of ending the terrible injustice of segregation," he said, adding it was West Point graduates who led the fight in the Civil War to "end the evil of slavery".

He failed to mention that one West Point barracks still bears the name of General Robert E Lee, who led the breakaway Confederate forces during that war, which brought an end to slavery.

Trump has rejected recent demands to rename US military bases bearing the names of Confederate officers