Lewis Hamilton beaten to pole by Nico Rosberg at Belgian GP
Nico Rosberg beat Mercedes team-mate Lewis Hamilton to pole position at the Belgian Grand Prix in treacherous wet conditions.
The two Mercedes were in a league of their own, more than two seconds faster than Red Bull's Sebastian Vettel in third.
Hamilton said he struggled with his brakes during the session and lost a lot of time slowing for Turn One.
Ferrari's Fernando Alonso was fourth, ahead of Red Bull's Daniel Ricciardo.
The Australian was fifth ahead of Williams driver Valtteri Bottas despite running wide at the high-speed Blanchimont bend.
Rosberg's pole sets up a fascinating race as the two Mercedes drivers head into the next chapter of their increasingly tense title battle.
The German leads his team-mate by 11 points going into the weekend but what could have been a major psychological blow to Hamilton will have been lessened as a result of Hamilton's problems.
Hamilton had a scrappy session, making mistakes on all of his flying laps in the top 10 shoot-out, while Rosberg was steadier and ultimately delivered a faster time, beating Hamilton by 0.228 seconds.
"It's awesome to be on pole," Rosberg said, "especially at this track. But it's only qualifying and there is a long race tomorrow."
Hamilton said: "I had a glazed front brake, so I was struggling under braking. I was losing massive amounts, especially into Turn One.
"You saw I kept going wide. It was only in Q3 I seemed to have the brakes not working, which takes your confidence away, but they'll scrub them this evening and they'll be fine for tomorrow."
What are glazed brakes?
"Glazing is when the brake pad surface ends up coated in crystallised friction material, affecting their stopping ability. It is usually caused when they have not been brought up to temperature properly."
BBC F1 co-commentator David Coulthard said: "Hamilton certainly looked out of sorts. It wasn't comfortable out there. But a disc doesn't glaze itself. The driver will have been involved in that process, too, so in the debriefs he will want to work out how that happened."
This weekend's race is the first after F1's four-week summer break and the magnificent Spa track in the Ardennes mountains is a fitting stage for Rosberg and Hamilton's battle.
Mercedes motorsport director Toto Wolff admitted the situation had required "a bit of mediating, management, caressing, hard words".
Behind them, Vettel recovered impressively after doing only 11 laps in Friday practice as a result of an engine problem.
The world champion edged out Alonso by just 0.069secs. The Spaniard was 0.994secs faster than team-mate Kimi Raikkonen in eighth place.
Both Ferraris ran a higher downforce rear wing, despite Alonso trying a low-downforce set-up in the morning session and saying he would prefer to use it if he could be sure the race was dry.
Ricciardo was just 0.125secs behind Alonso despite a massive 'moment' in Blanchimont, the Red Bull running wide and snapping alarmingly, the driver reacting quickly to stop a potentially major accident.
McLaren's Kevin Magnusen was seventh, three places and 1.1secs ahead of team-mate Jenson Button.
Felipe Massa was the other top 10 qualifier, guiding his Williams to ninth.
Williams had been expected to feature strongly at Spa, but the damp conditions hampered the team's performance as the car is quicker in a straight line than anything else but lacks ultimate downforce.