Belgian F1 GP: Nico Rosberg annoyed at himself over poor start

In the first race for F1's tweaked start rules - under which drivers are not allowed radio advice on the ideal clutch settings - Rosberg dropped from second to fifth on the run to the first corner at Spa.

Polesitter Hamilton meanwhile made a clean getaway and was eight seconds in front by the time Rosberg was back up to second place.

Although that gap came down as low as 2s later on, Hamilton always had enough in hand and stretched his championship lead to 28 points.

"I completely messed up the start, which was very annoying," said Rosberg.

"The start was really bad so I need to practice that a bit more.

"When I had clear air in the front, I chased Lewis, I was always coming close, apart from one phase in the second stint when he pulled away.

"I tried to hunt Lewis down but it wasn't enough."

Rosberg felt the extra formation lap required after Nico Hulkenberg's Force India hit trouble on the original grid was a key factor in his clutch handling going awry.

"We did another formation, which puts more temperature in and things change, that also caught me out," he said.

"But it's my job to do it well and I didn't do it well."

Hamilton said he never felt under too much pressure from Rosberg even as his team-mate gained.

"It was really just about utilising the tyres and not having to push on the out-laps," he said.

"I took it quite easy on three or four laps in areas when Nico could be closing, then I started pushing.

"I was never in a position when I was nervous."