The BBC reported on Thursday that the Mercedes board and motorsport director Toto Wolff, who also runs the Mercedes F1 team, were said to be open-minded about the possibility of supplying their former partner.
"McLaren has not dismissed the idea of looking elsewhere," reported the motorsport.com website, part of the Motorsport Network whose chairman is McLaren Technology Group's new executive director Zak Brown.
Mercedes had no comment.
McLaren said they would not comment on media speculation but a spokesman acknowledged pre-season had been "challenging and disappointing".
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"We are working with Honda to address shortcomings and deficiencies," he said. "Together with Honda we are considering options."
McLaren had a highly successful, championship-winning, partnership with Honda between 1988 and 1992 but the renewal of ties in 2015 has been troubled for a team that has not won a race since 2012.
Mercedes, who supplied McLaren between 1995 and 2014, have had the dominant engine of the new turbo hybrid era that replaced the old V8s in 2014.
With Lewis Hamilton and now-retired Nico Rosberg, they have won 51 of 59 races in the last three seasons with the Mercedes works team.
McLaren finished ninth in 2015 and sixth last season.
Honda had hoped to be more competitive this year but results from testing have been dire, with repeated breakdowns and McLaren completing far fewer laps than rivals with much slower times.
"We have only one problem, and that is the power unit. There is no reliability and there is no power," the team's double world champion Fernando Alonso told reporters last week.
'NO PLAN FOR HONDA SPLIT'
"I am driving at my best ... I feel the best driver out there, I just need an engine that can run as quick as the others on the straights," said the Spaniard.
McLaren's racing director Eric Boullier told reporters in Barcelona last week that there was "no plan at all" to split from Honda.
The Frenchman was also quoted by Spanish newspaper AS, however, as saying McLaren would be winning races with Mercedes engines.
Both sides have a long-term contract, and McLaren benefit from considerable funding from Honda, but renewed speculation about the partnership will put pressure on the Japanese manufacturer to resolve the issues.
(Reporting by Alan Baldwin, editing by Neville Dalton)
