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Sebastian Vettel and Lewis Hamilton have reignited the Ferrari versus Mercedes battle on the opening morning of F1 pre-season testing, with the German topping the morning session nearly half a second quicker than his rival.

After a frantic early morning roll call of pitlane launches and car reveals, action finally got underway at 9AM local time with defending F1 champion fittingly the first on track in the new W07.

On a damp track from overnight rain each team took tentative steps on installation laps with its fresh 2016 challengers. But once the sun broke through on to the Circuit de Catalunya the track quickly dried up, allowing all cars to run medium Pirelli tyres and subsequently lap times began to tumble.

Vettel and Hamilton traded top times throughout the morning session while Valtteri Bottas in the Williams slotted into a comfortable third in front of a tight midfield pack which could become the story of the 2016 season.

It would be Ferrari to top the morning session before the lunch break with a late lap of 1m 24.939s bettering Hamilton's best time of 1m 25.409s - but both cars are believed to have much more to give.

With a lonely Bottas third, 0.6s off Hamilton and almost three quarters of a second up on Red Bull's Daniel Ricciardo, Toro Rosso's Carlos Sainz rounded out the top five with the year-old Ferrari engines having ditched Renault.

The French manufacturer, who has taken over the former Lotus F1 squad in 2016, adapted to life in F1 slowly with Jolyon Palmer setting a 1m 31.351s which saw them end the session tenth.

Ahead, McLaren-Honda have already enjoyed 2016 possibly more than at any point in 2015 by ending the opening session sixth quickest overall with Jenson Button ahead of Marcus Ericsson in the 2015 Sauber.

New team Haas were given a rude awakening to life in F1 after Romain Grosjean suffered front wing failure on the main straight which curtailed his running on the team's debut outing, but he ended the session in front of Force India's new development driver Alfonso Celis.

With Renault completing the top ten, Manor's new configuration with a Mercedes power unit, Williams gearbox and DTM champion Pascal Wehrlein had a slow start to the test by completing just one timed lap in the session to slot into 11th.

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