Mercedes remain Ferrari's main focus despite the re-emergence of Red Bull in Barcelona, according to Sebastian Vettel.

The four-time world champion had to settle for third at the Spanish Grand Prix as Max Verstappen claimed victory on his Red Bull debut, taking Vettel's record as Formula One's youngest winning driver in the process.

Red Bull impressed in the testing that followed the race in Barcelona and expect to go well again in Monaco this weekend.

However, Vettel is not concerned about the progress of his former team and is only worried about Mercedes.

"I think our aim is still looking forward and, in that regard, our aim is still Mercedes," said the German.

"In Barcelona, we had a bad Saturday which explained a difficult race on Sunday. In terms of raw speed, I think we should have been ahead [of Red Bull], but we weren't.

"I think we have a strong package of new bits here and there and we obviously want to make progress and want to make sure we close the gap to Mercedes rather than looking at what's going on behind."

And Vettel hopes his experience in the principality can help secure a first race win since September 2015 in Singapore.

"It is one of the places where it is difficult to read the strength of the car or the weakness of the car," Vettel added.

"I think it is a place where the driver can make more of a difference, a place where you need to have the confidence as a driver to be able to make the difference.

"Of course, it is important which car you have [to determine] how confident you are, but the level of confidence going round the track, the trust in the circuit, is probably more important here because that allows you to extract a little bit more compared to 'normal' racetracks.

"The car is probably not as important here as it is in Barcelona, for example."