Lewis Hamilton expects another tough battle with Red Bull's Max Verstappen on Sunday despite securing pole position on an all-Mercedes front row at the Spanish Grand Prix.

Verstappen is now the six-time world champion's closest rival, the Dutchman 30 points behind after winning last weekend's 70th Anniversary Grand Prix at Silverstone and finishing second in the two races before that.

The 22-year-old will line up third on the grid, one slot higher than he had last Sunday when he came through to win with clever tire strategy while Mercedes suffered from blistering in the hot conditions.

"It's going to be tough when we get to the race," Hamilton told reporters in a video conference at the Circuit de Catalunya outside Barcelona.

"Over a single lap we seem to have the edge over the Red Bulls but this weekend we seem to be pretty much on par on race pace, so it's going to be a tough battle with Max."

Mercedes team boss Toto Wolff agreed with that assessment, based on the evidence from Friday practice, even if other elements were different.

"The only similarity between Silverstone and Barcelona this week is the ambient and the track temperatures," the Austrian told reporters.

"But the track itself is very different. So we don't expect the same blistering issues like in Silverstone but nevertheless more degradation and more overheating. And I believe Red Bull masters those conditions very well," Wolff added. 

"I hope we can give him a run for his money but definitely Max needs to be seen as the favorite based on yesterday's long runs."

Sebastian Vettel endured another difficult F1 qualifying session in Spain on Saturday with a Ferrari whose handling remained something of a mystery despite a change of chassis.

For the third time in six races, the four-time world champion qualified outside the top 10.

This time Vettel missed out on taking part in the final phase by an agonizing 0.002 of a second to McLaren's Lando Norris.

"It must be so tough for him mentally now...," commented 2016 world champion and compatriot Nico Rosberg on Sky F1 television.

"That's like 10cm at the end of the lap. For him, that must be very, very frustrating.

"I think he's in one of the most difficult mental challenges of his career at the moment."

Vettel, who has scored just 10 points compared to teammate Charles Leclerc's 45, is 13th overall and has only once started higher than 10th this year.

He is leaving Ferrari, after they decided not to renew his contract, at the end of the year with McLaren's Carlos Sainz coming in to replace him.

Ferrari replaced his chassis for Spain after detecting damage following last Sunday's 70th Anniversary Grand Prix at Silverstone, but it appeared to have made little difference.

"It's up and down, to be honest," he said when asked whether the car had improved.

"There are still some things that I can't really put an answer to. But I'm trying to do everything I can and ignore all the things that might not be right and do the best that I can. That's all I can do at the moment."

Leclerc qualified ninth and was also unhappy with the performance.