Top WorldSBK stars including five-time world champion Jonathan Rea expressed concern over the state of the surface at Argentina's San Juan circuit during free practice.

Laptimes were significantly down on the corresponding periods last year and some six second off the lap record set in 2018.

“It was really difficult to find a feeling out there because you cannot push anywhere near the limit. It is like riding on marbles and the track did not get much better," said Rea.

"I expected a big step in the afternoon session. Even though the track looked cleaner the grip wasn’t there. A really frustrating day because you are kind of reluctant to do anything with the bike set-up in readiness for the track ‘rubbering-in’ some more.”

Yamaha's Alex Lowes was equally as disappointed as he expected the surface to at least provide some grip in the afternoon.

It's really dirty and it hasn't improved as expected over the course of the day. The racing line is getting a lot better but if you get a bit offline then you're on to the dirty part of the track.

"Hopefully the line will get a bit wider ahead of the race tomorrow. It's a great track, the layout is fantastic, and the weather has been perfect today, but the problem with the dirty track means we're a lot slower than we should be.

"But then the conditions are the same for everyone and we just have to deal with them the best we can. This afternoon we tried something with the bike that didn't work as expected in the greasy conditions, which was important because now we know in which direction not to go tomorrow when, hopefully, track conditions improve."

Both Loris Baz, Sandro Cortese and Marco Melandri described the track condition as 'dangerous' with the German adding: "For me it's unbelievable that we're expected to race on a track in this condition. The track is beautiful, and the conditions were the same for everyone, but the surface dirt made it dangerous."

Former World Champion Tom Sykes was in agreement, saying: "It;s not safe and is so easy to get caught out, you can go 15cm off line and you are at risk of crashing which is far from ideal."

One man who did crash was Leon Haslam, who went down in strange, off-throttle highside: "I fell on an out lap, with zero-lean angle and zero brakes, as I had an off throttle high-side. It is the first time I had used that tyre. I went back out on my second tyre after the crash and I had zero grip. I could not even get to my knee because compared to the morning conditions they were a lot worse."