Lewis Hamilton says the prospect of Robert Kubica returning to the Formula 1 grid would be "great" for the championship.

The Polish driver's F1 career was put on hold after a rallying crash in 2011 but he appears to be edging closer to a return after completing two tests for Renault.

Kubica will drive one of the team's 2017 cars for the first time next week in the post-Hungarian Grand Prix test.

Renault have dismissed suggestions they are lining him up to replace Jolyon Palmer later this season, but Hamilton says he wants to see Kubica return to the sport.

"I'm really happy that he's doing the test, and I'll have a keen eye on how he's doing," said the Mercedes driver.

"I think it will be great if he's able to [return], if he can, physically.

"[He has] raw, natural talent, which I think as a sport it's a shame we don't have here with us."

The three-time world champion wants to follow Kubica's progress to see "how his tests are going" and "whether or not he's going to be racing".

Kubica finished fourth in the 2008 drivers championship while driving for BMW Sauber and led the points standings after winning the Canadian Grand Prix.

And Hamilton, who went on to win that year's title, believes Kubica would have been a rival at the front end of the grid had his career not been interrupted.

"Robert's one of the quickest drivers I've ever raced against," he added.

"If he was still racing today he'd been in contention for a world title, if he'd [already] not won one.

"Not a lot of great, great drivers come through.

"You have some that are much better than the rest, but still not the greatest, and then you have real special drivers like him."