The Kansas City Chiefs preserved their unbeaten start to the NFL season after blocking a last-gasp field goal to snatch a dramatic 16-14 victory over the Denver Broncos on Sunday.

The reigning Super Bowl champions looked poised to suffer their first defeat of the campaign after rookie Broncos quarterback Bo Nix expertly engineered a late fourth-quarter drive to the Kansas City 17-yard line.

That left Wil Lutz with what should have been a straightforward 35-yard chip shot to win the game with the final kick of an absorbing clash at Arrowhead Stadium.

But Lutz and the Broncos were left stunned after Chiefs' defensive end Mike Danna got a hand to the kick to block the attempt and leave Kansas City exhaling a collective sigh of relief.

Chiefs quarterback Patrick Mahomes raced across the field in celebration with his teammates as Kansas City sealed a win that sees them improve to 9-0 for the season.

"It just speaks to this entire team," Mahomes said of Kansas City's great escape. "I felt offensively we didn't do enough. Defensively we stepped it up in the second half, and then special teams – we're a full team. It's everybody, it was a special moment."

"Everybody believes, no one has any doubts, we just keep pushing and we found a way in the end," the 29-year-old Mahomes added.

The defeat was hard on Broncos signal-caller Nix, who had shown superb composure throughout to help Denver take a 14-3 second quarter lead thanks to touchdown passes wide receivers Devaughn Vele and Courtland Sutton.

Denver's defense, meanwhile, gave Mahomes and the Chiefs offense a torrid time, sacking the Kansas City quarterback four times.

Mahomes, though, gradually got his team back into the game, connecting with Travis Kelce for a touchdown that made it 14-10 at the half, before two Harrison Butker field goals in the second half gave them a slender 16-14 lead.

Nix then appeared to have done enough to give Denver a chance at winning the game, only for the blocked field goal drama to deny the Broncos a famous win. (AFP)