WASHINGTON, United States (AFP) — President Donald Trump on Sunday slammed the upset result of the Kentucky Derby, blaming the shock decision to disqualify wire-to-wire leader Maximum Security on “political correctness”.

“The Kentucky (sic) Derby decision was not a good one,” tweeted the US leader. “The best horse did NOT win the Kentucky Derby – not even close!”

Country House, a 65-1 long shot, won Saturday’s 145th Kentucky Derby after Maximum Security — initially thought to have taken the top spot — was stunningly disqualified for having hindered a rival horse.

“It was a rough and tumble race on a wet and sloppy track, actually, a beautiful thing to watch,” Trump wrote.

“Only in these days of political correctness could such an overturn occur.”

Maximum Security, the pre-race favourite, was running comfortably in front on the track in Louisville, Kentucky, but the colt moved sharply out from the rail as the field turned for home.

After an objection and a nail-biting 20-minute review by race stewards, he was ruled to have interfered with War of Will and other horses — a move ultimately judged to have significantly affected the outcome of the race.

It was the first time the horse that crossed the finishing line first in the Kentucky Derby was denied victory because of hindering another horse.