Honda boss Yasuhisa Arai says discussions over expanding its engine supply beyond McLaren are ongoing following the emergence of Red Bull as a potential partner for 2016.

With the four-time world championship winning team still without an engine deal beyond this season, Honda emerged as a potential candidate over the United States Grand Prix weekend.

However, while Honda is understood to be keen for a second customer in an effort to bring its under-developed power unit up to competitive speed ahead of more sweeping regulation changes for 2017, McLaren has expressed reluctance to share.

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Whilst Arai-san refused to give away too much detail - not least the team in question -, he insists discussions remain ongoing and that dialogue is open

"Obviously we cannot discuss details at this moment. We have been approached by the team but discussions are ongoing and nothing has been decided. I always say this season: we are always open, so we are on discussions that are ongoing - that's it."

Though McLaren has billed its relationship with Honda as exclusive, despite the Japanese firm's apparent agreement with FOM that it would be capable of adding to its roster from 2016, it isn't clear whether this comes in the form of an official veto or simply an unbinding agreement.