Red Bull team principal Christian Horner believes Mercedes will target Max Verstappen as Lewis Hamilton's Formula One replacement.

Seven-time world champion Hamilton recently agreed a one-year contract extension, but Mercedes are having to consider life after their star driver, who will be 37 next year.

Verstappen, 23, is seen as the natural heir to Hamilton's F1 throne, and although the Dutchman's current contract with Red Bull expires in 2023, a number of performance-related clauses could trigger his departure at the end of the year.

"I am sure that should Lewis decide to stop then Max will naturally be the driver at the top of Mercedes' list," Horner said on Monday.

"They also have George Russell and other drivers available to them.

"The reality is, that yes of course (there is) an element of performance-related clauses to Max's contract.

"But as with all these things, it is not about forcing a driver that doesn't want to be there."

Horner said "it is more about relationships than contracts" and that the relationship with Verstappen was "very strong".

"He believes in the project, in what we are doing, and he sees the investment that Red Bull is making," Horner said.

"I am confident that we won't need to refer to any contractual clauses. It will be down to us to deliver a competitive car."

Horner was speaking following an announcement that Red Bull will make their own engines from 2022 after agreeing to take over Honda's F1 operation.

Honda are leaving the sport at the end of the year, but the new deal allows Red Bull to continue using the Japanese manufacturer's technology, meaning they don't have to become a customer of rivals Ferrari or Renault.

The agreement with Honda will run through until 2025 when F1 introduces the next generation of engines. Last week, the sport announced a freeze on engine development from the start of next year.

Red Bull hope the move will enable them to take the fight to Mercedes who have won the past seven drivers' and constructors' championships.

Verstappen, who triumphed at last year's season-concluding round in Abu Dhabi, finished third in the overall standings, behind Hamilton and his Mercedes team-mate Valtteri Bottas.

"We demonstrated at Abu Dhabi that Mercedes are beatable at a track they have been unbeaten at for the past six or seven years," Horner added.

"We just need to be able to do that across the season. We are gathering momentum."

Hamilton will begin his bid for an unprecedented eighth title in Bahrain on March 28.