Top-seeded world number one Novak Djokovic beat powerful Austrian Dominic Thiem 6-3 6-4 in the fourth round at the Miami Open in Florida on Tuesday.

In a contest closer than the score might indicate, Djokovic needed four match points before finally prevailing against the world number 14.

Thiem, 22, the youngest player ranked in the top 20, regularly unleashed thunderous forehands that often had Djokovic on the back foot.

But Thiem could not capitalise on his chances. He converted only one of 15 break points, and in the end Djokovic's superior consistency proved the difference and he advanced after one hour 50 minutes.

Next up for the Serb is a quarter-final against Czech Tomas Berdych, who beat Frenchman Richard Gasquet 6-4 3-6 7-5 in an endurance contest that stretched nearly two hours 30 minutes under the scorching midday sun.

Another quarter-final will pit two big servers as Canadian 12th seed Milos Raonic takes on Australian 24th seed Nick Kyrgios.

Raonic, who lost the Indian Wells final to Djokovic nine days ago, demolished Damir Dzumhur of Bosnia 6-0 6-3 in less than an hour.

The often-volatile Kyrgios, meanwhile, kept his emotions in check as he edged Russian Andrey Kuznetsov 7-6(3) 6-3.