Red Bull team principal Christian Horner believes Honda is "very keen" to supply his team next season, but says McLaren boss Ron Dennis is blocking a deal.
Red Bull has yet to secure an engine contract for 2016 and has few options left after Mercedes and Ferrari ruled themselves out of a deal. The team approached Honda, which is the works supplier to McLaren, and in Mexico Honda boss Yasuhisa Arai said discussions are still ongoing.
However, McLaren has made clear it does not want its engine partner supplying another team and Horner admits a potential deal is in the hands of Dennis.
"I haven't spoken to anyone at McLaren other than Ron Dennis, who is the one guy who has the right of say there. His views were quite clear," Horner said. "I think the situation is, Honda are very keen but unfortunately they have a contractual status that is between them and McLaren and has nothing to do with us. It's for them to decide amongst themselves what they want to do."
Meanwhile, McLaren racing director Eric Boullier said Red Bull's engine predicament is not his team's concern.
"I'm going to repeat myself, as a partner we have to agree on strategies so this is not a question of trying to say 'Ron [Dennis] says no' or 'Arai says yes' there is no debate on this," he said. "Clearly there is an issue with Red Bull which was created by Red Bull and not by anybody else and we are not a charity foundation so we are not here to help.
"We are not going to go into this debate. Today there are discussions, but I think the position of McLaren-Honda has been clear."