SAKHIR, Bahrain (AP) — Veteran British driver Jenson Button will step in for Fernando Alonso at the Monaco Grand Prix next month.

Although the 37-year-old Button retired at the end of last season, he is taking Alonso's seat for this single race because McLaren has allowed the Spaniard to make his IndyCar debut at the Indianapolis 500 on May 28. Both races are on the same day.

"I'm thrilled to be making a one-off return to Formula 1 racing, and I couldn't think of a better place to make that return," Button said in a team statement on Friday. "I've won the race before, in 2009, and it's one of my all-time favorite racetracks. It's a tricky street circuit on which a good driver can really make a difference and, although the McLaren-Honda MCL32 hasn't begun the season well, I think it may be more suited to Monaco than to the faster circuits."

Button is oozing confidence he will be fit enough despite the six-month gap from his last F1 race.

"I'm supremely fit, having done a lot of triathlon training recently, so I have no worries on that score," he said. "I'll drive the MCL32 around Monaco in the McLaren sim(ulator) beforehand, and I reckon I'll be ready."

Alonso retakes his seat for the race after Monaco — the Canadian GP on June 11 — and for the remainder of the season.

McLaren has yet to score a point after two races — Australia and China — following a frustrating campaign last year where the team struggled to adapt to the Honda engines.

"I realize we won't have a realistic chance of repeating my 2009 victory, but I think we'll have a opportunity to score world championship points," said Button, who will race alongside teammate Stoffel Vandoorne.

"I was truly delighted when Jenson accepted our suggestion that he race at Monaco," McLaren's racing director Eric Boullier said. "Jenson is a class act. He's a superb driver, fast, smooth and precise, and he won't have lost any of his competitive edge over the past few months. He'll do a great job for us, I'm sure of that."

Button's farewell race at last season's Abu Dhabi GP ended badly when he had to retire with a suspension problem. Although Button, who is still contracted to McLaren, also has an option to drive for the team in 2018, he said at the time that he did not expect to come back.

Button was widely expected to take Alonso's seat at Monaco. Other drivers were already saying how excited they were by his potential return, even before Friday's announcement.

"I think it would be great for the sport to have Jenson back in," said three-time F1 champion Lewis Hamilton, who raced alongside Button at McLaren before joining Mercedes in 2012. "I like Jenson, I still think he is one of the best drivers ... his caliber is still higher than any other driver who could take that spot, for sure."

The 35-year-old Alonso's motivation is part of a wider ambition that also includes the Le Mans 24 Hours endurance race.

McLaren is back in the Indianapolis 500 for the first time in 38 years with Alonso's entry, a Dallara DW12 chassis run by Andretti Autosport. Team owner Michael Andretti is a former IndyCar champion who raced in Formula One for McLaren in 1993.

Alonso flies to Alabama next week to visit his IndyCar team members and then have a seat fitting done. After the Russian GP on April 30, his schedule will become even more hectic.

"After Russia, I will try to be in Indianapolis for a couple of simulator days and hopefully test the car, but it's not 100 percent sure," Alonso said. "After that I will go to the Spanish Grand Prix (May 14) and then fly to America on Sunday after the race."

Boullier is excited at the challenges facing Alonso.

"I hope he'll have some great stories to bring back to us from Indianapolis. You couldn't get two more different racetracks than Monaco and Indy," Boullier said. "That's the beauty of our sport. It also reflects the technical versatility of McLaren and Honda. And it underlines the fact that we're racers, above everything else."