Fernando Alonso has indicated he will leave McLaren-Honda at the end of the year if he does not see signs they can be competitive by September.

Axar.az reports citing BBC Sport.

The two-time world champion is out of contract at the end of this season.

"We have to win," he said. "If we are winning before September, when I will make a decision, I will stay."

When pointed out this was unlikely, he said: "I joined this project to win the title. If you are not in a competitive position, maybe you change project."

However, the Spaniard said he had not yet started to think seriously about his future.

"Until I sit down with myself in September, I cannot say for sure," Alonso said.

Alonso joined McLaren at the start of 2015, when they began their relationship with engine partner Honda. But the team have been uncompetitive for all three years, largely because of a lack of performance from the Honda engine, and that is causing tension within the team.

McLaren executive director Zak Brown said on Wednesday that he had "serious concerns" about Honda, which he said appeared "lost".

He added that the McLaren-Honda relationship was nearing "a fork in the road" and that McLaren were "not going to go into another year like this, in hope".

Alonso said: "We all want to win and Zak's comments about Honda is what you would expect him to say. He wants to win, he wants McLaren to win and things have to change."