McLaren are "considering options" amid reports they have sounded out Mercedes about becoming their engine suppliers again.
The troubled performance of Honda's new power unit in winter testing has led to speculation over the future of their partnership with McLaren just three years into a long-term deal.
According to reports, McLaren have made an initial inquiry with Mercedes, their former engine providers, about the possibility of a reunion if they decide they cannot continue with Honda.
McLaren declined to comment on the specific reports when contacted by Sky Sports, but did say they were "considering options" with Honda as they attempt to turn the situation around.
"Winter testing was challenging and disappointing," said a McLaren spokesperson.
"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 declined to comment.
According to the BBC, 'McLaren's contact with Mercedes was characterised by sources as informal and brief and has not led to any resolution on either side. But the Mercedes board and motorsport boss Toto Wolff are said to be open-minded about the possibility of supplying their former partner.'
And Motorsport reported: 'While meetings have taken place since Barcelona testing to try to push Honda to take action needed to lift its engine program, McLaren has not dismissed the idea of looking elsewhere.
'One avenue is the customer Mercedes engine supply that had originally been earmarked for the Manor team, and perhaps could be ready as early as later this season if Honda shows no signs of improving.'
How big are the cracks in the McLaren-Honda marriage?
The reports have surfaced just days after Eric Boullier, McLaren's racing director, told the Spanish press the team would win races in 2017 if they had a Mercedes engine, which is considered to be the best in the field.
Asked directly by AS if he believed McLaren would be winners if they were armed with Mercedes power, Boullier replied: "I think we would."
Despite redesigning their engine for 2017 in a bid to compete with Mercedes and Ferrari, Honda experienced repeat reliability problems in winter testing with McLaren completing the fewest laps of any team.
Fernando Alonso, who returned to McLaren in 2015 with the aim of winning the world title, pinned the blame for the team's troubles on the engine, saying it had "no reliability" and that there was "no power".
Responding to an initial round of speculation at testing that McLaren could look for an early way out of the deal if the situation did not improve quickly, executive director Zak Brown told Sky F1 last week the team would stay loyal to Honda as "that is what McLaren do".
Back to the future - again?
McLaren reunited with Honda two years ago aiming to recapture the glory of their first period in partnership, when they dominated F1 in the late 1980s and early 1990s.
McLaren ran Mercedes engines for 19 years and won three Drivers' and one Constructors' Championship, but the German carmaker launched their own works team in 2010 after buying Brawn GP. McLaren continued to use Mercedes power in a customer capacity until 2014 before luring Honda back to F1 to re-establish themselves as a works operation.
Despite a dismal start to their Honda reunion, then-McLaren CEO Ron Dennis told Sky F1 in March 2015: "If your objective is to win a World Championship, you have to have a strong OEM [original equipment manufacturer] behind you which has the technology and capability to produce a winning engine - and that's what Honda has, they've proven it many times."
F1's other engine providers, Mercedes, Ferrari and Renault, all currently supply engines to three teams, including their own respective works outfits. However, there is theoretically one more Mercedes engine supply open after Manor folded over the winter.
But were McLaren to seriously consider an early termination of their Honda deal, it remains to be seen how easy it would be to unpick their long-term agreement given the Japanese firm's substantial commitment to the team.
Speaking after a difficult fortnight of testing, Honda F1 chief Yusuke Hasegawa said: "The winter test as a whole has been tough for us, however, it's also true that the team has worked incredibly hard to make progress and I'm very thankful to each and every one of them. They have done McLaren-Honda proud.
"We still have some more time before Melbourne and we'll continue to work tirelessly with McLaren right up until we board the plane for Australia."