It's the ultimate symbol of American politics under Donald Trump – a blood-soaked cage match on the lawn of the White House for the US president's 80th birthday. A giant arena dubbed "The Claw" has been built on the famed South Lawn for Sunday's tournament featuring 14 Ultimate Fighting Championship (UFC) contestants. Critics have panned the unprecedented $60 million "UFC Freedom 250" event as tone-deaf at a time when Trump's war in Iran has sent the cost of living soaring for ordinary Americans. Trump says it is a great way to kick off the 250th anniversary of American independence – not to mention his own birthday – and insists UFC is bearing all of the cost. But the billionaire Republican is also reveling in the macho side of an event that will see bare-knuckle fighters battle it out in a mesh-framed cage known as the "Octagon." "They're the roughest people you'll ever meet," Trump told the New York Post on Thursday. "If you haven't seen it much, you're not going to believe it." Trump has close ties with the violent sport's leaders and has attended several previous fights, endearing himself to its fanbase of young men who were also crucial to his own political rise. Secretary of State Marco Rubio also hailed the event as he signed a partnership deal with UFC boss Dana White to promote mixed martial arts internationally. "That's what Sunday is about, it's a gift to the American people," Rubio said on Thursday, adding that it would be watched by "probably a billion people all over the world." It will certainly be unlike any other event in the White House's 200-year history. Around 4,000 people will watch the match inside the arena itself, with Dana White saying more than half would go to members of the US military. Another 125,000 are expected to see it on a giant screen on the Ellipse, a green space just outside the White House.