Valtteri Bottas topped the first morning of the two-day post-Spanish Grand Prix Formula 1 test for Mercedes.
Bottas set a best time of 1m16.625s using the C3 Pirelli tyres, which were the softs for last weekend's Spanish Grand Prix weekend, shortly before midday.
This consolidated his advantage at the top of the timesheets over Ferrari driver Charles Leclerc, who had earlier led the way.
Leclerc improved his time shortly afterwards, also using the C3 tyres, to close to 0.797 seconds behind.
Bottas subsequently set the fastest times of the day in each sector, although he did not put them together on the same lap so his time did not improve.
McLaren driver Carlos Sainz Jr was third fastest using the C2 Pirellis, just 0.021s faster than the similarly-shod Red Bull of Pierre Gasly.
Gasly completed 77 laps during the four hours of running, more than anyone else.
Ferrari fielded a second car in Spanish GP specification for Pirelli test work, with Sebastian Vettel driving and ending up fifth fastest using unmarked test tyres.
Toro Rosso driver Daniil Kvyat was sixth fastest using C3 rubber ahead of Pietro Fittipaldi for Haas.
The Brazilian made a series of improvements in the final hour before lunch using C3 rubber, working his way down to a 1m18.643s.
Racing Point driver Sergio Perez was eighth fastest in the second Pirelli test car, ahead of Renault driver Nico Hulkenberg.
Hulkenberg had a quiet morning, completing only 12 laps early on before taking his tally to 22 and improving to a 1m20.239s before lunch.
Racing Point simulator driver Nick Yelloly made his first F1 on-track appearance for four years and ended up 10th fastest, just ahead of Alfa Romeo's test debutant Callum Ilott.
Ilott focused on running on C2 rubber, setting his best time with just under 40 minutes remaining.
F2 championship leader Nicholas Latifi returned to action for Williams ahead of his planned Friday practice appearance during next month's Canadian Grand Prix weekend.
He set a best time of 1m21.008s, 4.483s off the pace, using C2 Pirellis.
Tuesday morning times
|3||Carlos Sainz Jr.||McLaren/Renault||1m18.263ss||1.738s||64|
|4||Pierre Gasly||Red Bull/Honda||1m18.284ss||1.759s||77|
|6||Daniil Kvyat||Toro Rosso/Honda||1m18.597ss||2.072s||57|
|8||Sergio Perez||Racing Point/Mercedes||1m19.719ss||3.194s||66|
|10||Nick Yelloly||Racing Point/Mercedes||1m20.609ss||4.084s||55|
|11||Callum Ilott||Alfa Romeo/Ferrari||1m20.683ss||4.158s||31|