SILVERSTONE, England (Reuters) - Max Verstappen has a contract with Red Bull to 2028 but the chances of the four-times Formula One world champion seeing it out are looking increasingly slim with team boss Christian Horner accepting next year, if not this, could be make or break.

Speaking at the British Grand Prix, Horner confirmed the existence of performance-related clauses that the sport's most sought-after driver can activate to leave early.

While Verstappen might be able to trigger them in a matter of weeks, according to some sources, it would be a gamble with a major chassis and engine change -- the biggest for decades -- coming in 2026.

One popular view in the paddock, despite constant speculation about a move to Mercedes, is that the Dutch 27-year-old is more likely to wait and see which way the wind is blowing before deciding for 2027.

"2026 is going to be a transformational year. It's the biggest rule change in Formula One probably in the last 50 years where both chassis and power unit are being introduced at the same time," said Horner.

"Nobody, with hand on heart, can know what the pecking order is going to be... It could be Ferrari. It could be Mercedes. It could be anyone.

"It'll only be really this time next year that you'll have a clear indication of what that pecking order is. So, there are no guarantees that jumping into a Mercedes car would automatically be a better proposition."

VETTEL EXAMPLE

That said, and despite claiming Verstappen wanted to see out his career at Red Bull, Horner offered a history lesson to illustrate that Red Bull was prepared for change regardless.

He recalled how Sebastian Vettel, another four-times Red Bull world champion, had joined Ferrari a year after a major rule change in 2014 had begun an era of Mercedes domination and Red Bull struggled with an uncompetitive Renault engine.

"I remember (the late Red Bull co-owner) Dietrich Mateschitz telling me at the time 'We don't need the best driver if we don't have the best car'," said Horner.

"At that stage, it was about building a team... things go in cycles and sport goes in cycles."

Red Bull seem to be already in just such a cycle, their 2023 domination slipping away last year along with design genius Adrian Newey, now at Aston Martin. The Honda engines are going the same way from 2026.

Highly influential engineering head Rob Marshall is at champions McLaren while Red Bull's veteran consultant Helmut Marko is 82. Vettel has already been mentioned as a possible replacement.

Horner's own position has been questioned, with Verstappen's father calling last year for him to go after allegations of misconduct were made by a female employee. The Briton denied them and was cleared after an investigation.

"We've had two incredibly successful cycles in Formula One, and what we want to do is build towards the next cycle," said Horner, who also sang the praises of 17-year-old talent Arvid Lindblad.

"Now, of course, we want that to be with Max, but we understand the pressure that there is next year, with us coming in as a new power unit manufacturer. The challenge of that is enormous."

Red Bull are building their own engine, bringing everything under one roof in a bold move against major manufacturers with vast resources and years of experience in the field.

"To expect us to be ahead of Mercedes next year... it would be embarrassing for Mercedes if we were, or for any manufacturer," said Horner.

"But I think we're going to be in a competitive position, potentially even to where we are today relative to our other PU (power unit) manufacturers. There's everything to play for."

How long Verstappen stays for the ride remains to be seen.

(Reporting by Alan Baldwin, editing by Pritha Sarkar)