Donald Trump has defended himself on Twitter after he was filmed walking unsteadily down a ramp on Saturday.

The US president appeared to be unsure of his footing as he walked away after delivering a speech at West Point Academy, prompting social media critics to question if it was a sign of failing health.

However, Mr Trump wrote on Twitter that the ramp was 'long & steep, had no handrail, and most importantly was very slippery’.