Defending champion Cameron Norrie lost in straight sets to Argentine qualifier Mariano Navone in the semi-finals of the ATP Rio Open.

Norrie, 28, was aiming to win back-to-back titles at the Brazilian clay court tournament after defeating Carlos Alcaraz in last year's final.

But the British number one struggled in hot and humid conditions in Rio.

The 22-year-old Navone, ranked 113th in the world, won 6-4 6-2 to reach his first ATP final.

He will face compatriot Sebastien Baez after the world number 30 won 7-5 6-4 against another Argentine, Francisco Cerundolo.

Both Navone and Norrie broke serve in the opening two games before Navone gained the decisive break in the seventh game of the first set.

They exchanged breaks again at the start of the second set, and Navone broke Norrie once more in the third and fifth games before closing out the win.

"It's incredible," said Navone. "I played so good all week. Today was very hot and humid, it's tough to play in these conditions, but I've played six matches in a row so I feel pretty good."

This was Norrie's second tournament since reaching the last 16 of the Australian Open, having fallen at the first hurdle against world number 106 Federico Coria in Buenos Aires.