Vettel has a nine-point lead over Hamilton in the drivers' standings and is 23 points in front of Bottas.
Few had tipped Ferrari to be in race-winning contention this season, but the four-round extra-European prologue to the 2017 F1 season was a finely balanced fight between the Scuderia and three-time constructors champion Mercedes.
Hamilton was 0.029 seconds quicker than team-mate Valtteri Bottas, and a second clear of Ferrari's Kimi Raikkonen and Sebastian Vettel in third and fourth.
Last year's victor Dutch teenager Max Verstappen, who triumphed on his debut for Red Bull, was fifth fastest ahead of his team-mate Daniel Ricciardo, Kevin Magnussen and his Haas team-mate Romain Grosjean, Nico Hulkenberg of Renault and Carlos Sainz of Toro Rosso.
Verstappen's biggest incident of the afternoon was a slide and trip through the gravel at Turn 9 early on, which the team attributed to a gust of wind. Red Bull is thought to be bringing further updates throughout the weekend, so judging the success of the so-called B-spec RB13 on FP1 pace alone would probably be a bit premature. The team endured two very hard years after Honda were unable to supply a competitive power unit and 2017 was expected to be a major step forward; but the engine manufacturer is once again way off the pace.
"I didn't get everything together, I wasn't too happy but I can feel the vehicle is quick so that is good".
And asked if he agreed with the assessment of former Ferrari driver Felipe Massa that the Scuderia would throw the bulk of their support behind Vettel, Hamilton told Sky Sports News HQ: "I think they are always like that".
"The season will start new", he said.
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"This inter-team battle is a totally different situation that what we have seen over the last three years", Wolff said.
Nico Rosberg, the victor of the first four races in 2016, won the title with Mercedes last season, while Hamilton won the previous two championships.
But by the end of turn two, the first proper corner on the track, it was Bottas who led the race after a flying start saw him overtake both Ferraris.
"I think Ferrari has, in general, being very good in managing the tyres, so we have been focusing on getting a good long runs' pace to try and do better this weekend".
Since debuting at the Spanish Grand Prix in 1977 as Williams Martini Racing, only Ferrari and McLaren can boast more than their tally of 114 wins - although the last of those came in Spain for Pastor Maldonado five years ago.
After failing to start in Russian Federation, he is just hoping his revised McLaren will be on the grid to take part in his home race this Sunday.
"Bottas was quicker because he won the race but Lewis is an outstanding talent, a world champion", said the the F1 legend.
But Hamilton arrives at the fifth race of the season facing new challengers from both within and without.