Honda had the capacity to supply a second Formula 1 team with engines in in 2016, despite McLaren's Ron Dennis suggesting otherwise.
Having asked to terminate its contract with Renault at the end of last year, Red Bull turned to Honda for an engine supply after Mercedes and Ferrari both decided against stepping in.
But in November, Honda motorsport chief Yasuhisa Arai said it was too late to provide a supply, with Red Bull ultimately concluding a deal to stay with Renault.
McLaren Technology Group CEO Ron Dennis said there was not the capacity to support another team, a decision "fully supported by Honda".
But Autosport understands Honda had the capacity to supply a second team, and Arai said it is open to the possibility of such a scenario from 2017 onwards.
"We are always open to supply a customer team," Arai told Autosport. "The year of 2017 and 2018, we are always open."
Arai said Honda would discuss any customer supply with McLaren should a request be made.
"We can't go into details of the contract, but we do have to discuss as a team beforehand," he said.
"If there is a request or if we are thinking about offering to a second or third team, we will always openly discuss with McLaren."
Poor performance and reliability blighted Honda's return to Formula 1 in 2015, with McLaren finishing ninth in the constructors' championship with just 27 points.
When asked if he felt supplying a second team would aid Honda, Arai said: "I don't think so because the 'size zero' concept is unique to McLaren-Honda so whether that power unit will work with a customer team, we don't know.
"One thing I can be sure of is that if we had a second team the progress in reliability would increase but I don't know about performance."