Fernando Alonso
Fernando Alonso's imminent arrival at McLaren has left Jenson Button's future in jeopardyGetty

Fernando Alonso will be officially unveiled as a McLaren driver on Thursday morning (11 December) as the English side is expected to announce its 2015 drivers' line, reports in Spain have claimed.

After Ferrari announced the Spaniard's departure earlier last month – while appointing Sebastian Vettel as his replacement at the same time – Alonso had been tipped to return to McLaren.

Reports have since claimed Alonso has signed a two-year contract worth £25.5m a year but the confirmation was delayed as McLaren waited to make a decision on whether Jenson Button or Kevin Magnussen will partner the Spaniard to complete the line-up.

McLaren will announce that decision during a news conference at its Surrey factory.

Spanish newspaper AS assure the English side will confirm Alonso as his new driver while the Spaniard will be accompanied by his new teammate.

AS believes Magnussen is in pole position to partner Alonso next season.

Speaking recently about his future at McLaren, Button made it clear he would only be interested in staying in the sport if he had a race-winning car.

"I want to race in Formula One. It's still a question I can't answer," he told Sky Sports News.

"I think for all of our sakes, it's better sooner rather than later. If I'm in Formula One next year it's an exciting challenge with the new engine and new era with the team. If I'm not, I've got other exciting challenges that I want to focus on so I wouldn't worry about me. But as I say, it would be nice to know sooner rather than later."