Jenson Button has admitted the chance to re-unite with Honda in 2015 is the sticking point that is delaying a new contract extension with McLaren for 2014.
As the team line-ups for 2014 begin to take shape McLaren remains one of the last teams to confirm who will be driving the MP4-29 next season.
Though it is widely expected Button will remain with Sergio Perez next season there has been rumours Felipe Massa is in talks with the Woking based team.
A McLaren spokesman said this week: "We don't comment on media speculation with regard to rumoured driver movements."
The 2009 champion himself had been mentioned quietly as possible targets for Red Bull and Ferrari before both teams announced Daniel Ricciardo and Kimi Raikkonen respectively for next season.
Speaking to AFP Button said staying at McLaren was now a "formality" but it's the option of staying for 2015 that is stalling talks as McLaren want driver certainty heading into the new Honda era.
"We've shown in the past that we weren't afraid to make the changes that we felt that we needed to in the team, whether it was inside the organisation or in the driver lineup, in order to get the job done," McLaren Managing Director Johnathon Neale told a Vodafone teleconference.
Button hinted at an ExxonMobil promotional event ahead of the Singapore Grand Prix that 2015 is the sticking point.
"Nothing's sorted yet for the year after," he said, referring to 2015.
"2014 is an option year on the previous contract and then we see."
Despite all the talk McLaren has said that a decision will be made "pretty soon" and when it comes to deciding the line-up for next year 2015 won't be a major factor.
"More than anything else what you really want is talent and high performance," Neale added.
"We've shown in the past that we weren't afraid to make the changes that we felt that we needed to in the team, whether it was inside the organisation or in the driver lineup, in order to get the job done."
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