Red Bull Racing team boss Christian Horner has fired a warning shot across the bows of his Formula One rivals by claiming that there is a lot more to come from the race-winning RB5 over the remainder of 2009.

Speaking after Mark Webber's Spanish Grand Prix podium, which confirmed RBR as best of the rest behind Brawn GP in the first third of the season, Horner confirmed that, having been run until now without either KERS or a version of the controversial 'double decker' diffuser, the car could be made a lot more potent.

"We have the first pole position out of the way, and have the first win out of the way, and that automatically changes our focus," Horner told the official F1 website, "Our focus now is very clearly to close the gap to the Brawns. Barcelona has shown that we have done that - and we still have a lot more development potential open to us. The car is performing very well, the team is performing exceptionally well, and we are going in the right direction.

"Adrian Newey and his crew have done an exceptional job. They have chosen a very intelligent interpretation of the regulations - in typical Adrian fashion - and he has pushed the boundaries and the limits and produced a very innovative car, but also a very attractive car. I think that the solution they came up with to the regulations as we understood them is impressive. And there is now further clarity on the floor regulations which opens up some exciting development opportunities for us."

While impressing without the sort of diffuser used by Brawn, Williams and Toyota to good effect in the first three races of the year, Horner confirmed that work is continuing to produce a new underbody for the RB5 in time for next weekend's Monaco GP.

"It is a big challenge for us to incorporate a new floor given the characteristics of the RB5 - probably more difficult than at other teams - but be assured that the guys back home in Milton Keynes are working very hard on a solution and, hopefully, Monaco will be its first race," he revealed, without going into detail about the amount of work required to circumvent the car's slim rear end and pullrod suspension.

While happy to accept praise for the RB5, however, Horner is also keen to underline the impact his 2009 driver line-up has had on results, with Sebastian Vettel and Webber currently holding down third and fourth places in the championship.

"Sebastian is in extremely good form at the moment and is doing a fantastic job while, if you consider what Mark had to deal with [over the winter] - a broken leg, and a broken shoulder that he had forgotten to tell us about - he has made a remarkable recovery and put all the malaises behind him," he commented, "I must say that we have a very strong driver pairing."

Vettel's form has naturally led to him being linked with other teams - albeit ones currently in Red Bull's shadow - but Horner is confident he can retain his line-up into 2010.

"Sebastian is very happy driving for this team - and we are very happy to have him," he stressed, "He has been a member of the Red Bull family for a long, long time and Red Bull Racing has provided him with a very good car this year. I think that Mr Mateschitz has mentioned that Sebastian is certainly not for sale.

"I'm obviously not disclosing the details of his contract, but I can't imagine anywhere else that Sebastian would rather be at the moment - and, for next year, I don't see any intention that he goes anywhere else. He is a fixture within the team."