McLaren have admitted they and engine suppliers Honda are exploring all options as they attempt to solve their reliability issues ahead of the new Formula One season.
The British team are in the third of a 10-year deal with Honda but the partnership is in crisis ahead of the new campaign after a dour eight days of pre-season testing.
McLaren completed the least mileage of all 10 teams in Barcelona, while the Honda engine is also down on speed.
Racing director Eric Boullier said he thought McLaren "would be winning again" if they switched to former supplier Mercedes and r eports on Thursday claimed an approach to the German company had been made.
McLaren and Mercedes enjoyed a near two-decade relationship that came to an end after the 2014 season.
The former would not comment on the Mercedes approach but confirmed they were looking at all their options.
A McLaren spokesman said: "Winter testing was challenging and disappointing. We are working with Honda to address shortcomings and deficiencies. Together with Honda we are considering options, but we will not comment on media speculation."
Mercedes would not comment when contacted by Press Association Sport.
McLaren, who have won a combined 20 drivers' and constructors' championships, h ave not won a race since Jenson Button triumphed at the Brazilian Grand Prix in 2012.