Novak Djokovic joined his great rivals in the semi-finals of the French Open as the dominance of the top seeds reached its seemingly inevitable conclusion.

World number one Djokovic is still to drop a set after a 7-5 6-2 6-2 victory over Alexander Zverev and he will take on fourth seed Dominic Thiem, who defeated Karen Khachanov 6-2 6-4 6-2 to reach a fourth successive semi-final at Roland Garros.

With Rafael Nadal taking on Roger Federer in the other semi-final, the top four seeds are all through to the last four for the first time at a grand slam since the Australian Open in 2012.

Remarkably, it is the first time at a slam since the French Open seven years ago that Djokovic, Federer and Nadal have all made it through to the semi-finals.

Djokovic said: "It speaks about the quality of the tournament and the quality of the top four guys that reached the last four.

"I think it's great to have the top four players competing in the semi-finals at the biggest event because it brings even more rivalry, more importance to those matches and to the tournament in general.

"Dominic is deservedly where he is, one of the top four guys, especially on clay. He's got that tremendous power in his game, especially with forehand and serve. I think backhand also has improved a lot in the last couple of years.

"If he continues playing this way, not just on clay, I think we will probably be seeing him more often on different surfaces in the final stages of the tournament.

"It's a different time for us now than it was five years ago, obviously. We're a bit older. But we have still been enjoying some of our best tennis in the biggest events, talking about Federer, Nadal, and myself. That's great to see."

Djokovic's win over Zverev was his 26th in succession at the slams. Two more wins will see him become the first man in the Open era to hold all four titles for a second time.

"I think the further I go in my career, the sense of history-making is only getting stronger," said Djokovic. "That's one of the greatest motivations I have.

"I think there is no better way to make history of the sport than to win slams and play your best in the biggest events, and obviously try to stay number one as long as you can."

Djokovic and Thiem faced each other in the semi-finals in 2016, with the Serbian winning easily, but Thiem turned the tables the following year in the quarter-finals before reaching his first grand slam final here last year.

The Austrian has played himself into top form after a difficult start to the tournament but, like other hopefuls before him, finds himself with a formidable road to the trophy.

"It's incredibly difficult to win a grand slam," he said. "Because especially for us players who didn't have one yet, if everything goes quite normal, we have to beat two players with 15 or more grand slams.

"But I will step on the court tomorrow, try everything, of course, give everything. I hope it's going to be positive in the end, but the challenge is huge. Novak is in very good shape again, probably playing his best tennis of his life.

"I'm in the semi-finals with maybe the three best players of all time, so everybody can see how tough the way is for me."

Thiem was utterly dominant against Khachanov while the only alarm for Djokovic came when he dropped serve to leave Zverev serving for the first set.

But the German could not take his chance and from then on the result looked inevitable.

This has been Zverev's best grand slam tournament after a couple of years of underachievement, but there was little sense of satisfaction.

He said: "It's been nice, but I feel like I'm at a stage where, quarter-finals, I could go further. From the seedings, I should be in the quarters. I hoped more from this match, really. But once the first set slipped away, it was kind of difficult to play him."