Hamilton won six of the last seven races before F1's summer break

Lewis Hamilton says scoring points will be difficult in what will be a "very, very hard race" from the back of the grid in Sunday's Belgian Grand Prix.

The Mercedes driver has been hit with a series of penalties for using too many engine parts.

Hamilton has a 19-point championship lead over team-mate Nico Rosberg.

He said: "I envisage it will be hard to get into the top 10. All I can do is to aim as high as possible. A podium feels unlikely but it's not impossible."

Hamilton said his attempt to fight back through the field would be made more difficult by the fact that the Pirelli tyres are not lasting at the Spa-Francorchamps track.

There are unexpectedly high temperatures at the fast and demanding circuit in the Ardennes mountains this year and high tyre pressures chosen by Pirelli to protect against failures following two high-speed blowouts at last year's race are exacerbating the situation.

"With these tyres the way they are, which is a bit of a mess, it is going to be tough out there for everyone," Hamilton said.

"It's a long race. I don't have to go crazy at the start. That's the same whenever we start at the back.

"There were failures last year and they didn't want failures this year so they put the pressures up to 23, 24psi whatever it is. It's so high. I have never seen pressures like that my whole racing career. That doesn't help."

Hamilton said the problems caused by the tyres would make chasing other cars more difficult. The Pirellis overheat and lose grip if a driver follows another car closely. This has the corollary of reducing the number of laps the tyres can manage.

"It is going to be a very, very hard race," he said. "Being this hot it is going to be hard to follow. Being in the traffic it is going to be hard to get to my stop target, or go longer than the guys in front of me.

"But I hope I prove myself wrong and I hope I'm pleasantly surprised."

Hamilton's remarks on the tyres were echoed by McLaren driver Jenson Button, who said the pressures were "unbelievably high".

"It is amazing what we have to do to get the tyres in the working window," said Button, who starts ninth.

"If you push on the out lap (from the pits), they are done by turn three, blistering and overheating. What we have to do is crazy. I have never had to do this in my career before.

"It's the pressures. It's not helped by the temperatures, but we go to hot countries and Pirelli know that.

"It is shame we are so high on the pressures because we are in a position at the moment with the tyre where you can't push the car. You are just rolling around with the tyre.

"Hopefully with the new tyres for F1 next year it will not be the case because it is not a nice feeling at the moment."

Pirelli has been set the task of providing tyres in 2017 that drivers can push flat out for entire race distances, as opposed to having to lap under the limit to ensure the temperatures remain under control, as is the case currently.