Donald Trump has responded to Joe Biden's announcement he will run for the Democratic presidential nomination by mocking the veteran politician's intelligence and claiming he will compete against "very sick" rivals with "demented ideas".
"Welcome to the race Sleepy Joe. I only hope you have the intelligence, long in doubt, to wage a successful primary campaign," Mr Trump tweeted.
"It will be nasty - you will be dealing with people who truly have some very sick & demented ideas. But if you make it, I will see you at the Starting Gate!"