Team chiefs Eric Boullier and Ron Dennis are focusing their efforts on securing the two highly-rated F1's top stars as soon as they can.
Although both drivers are under contract for the immediate future - with Vettel committed at Red Bull until the end of 2015 and Alonso a year longer at Ferrari - that has not proved a turn-off for McLaren.
In fact, the team is eager to get a firm commitment on both drivers' plans over the next few years, and has told them it is ready to wait until 2016 or 2017 for them if it must.
Getting such a commitment now would then allow it to finalise driver plans in the shorter term, or even open the door on a deal being reached to land its big star earlier.
This is why McLaren is refusing to sort out its 2015 line-up until it knows exactly what Vettel and Alonso are doing longer term, which means current drivers Kevin Magnussen and Jenson Button are being left in limbo.
Speaking exclusively to AUTOSPORT, racing director Boullier made it clear that McLaren was doing all it could to win over Vettel and Alonso, and would refuse to give up its chase until both drivers had categorically said no.
When asked about the chances of getting one of the big star names, Boullier said: "I will try any driver that will suit our strategy for the future.
"We are still pushing and we will take the time we need. We don't want to do a mistake - we have one shot and we don't want to miss it.
"McLaren is a top team, a big team, with a lot of history and we want to be back where we should be.
"So if we can afford to take the time to think and to prepare our strategy then we have to do it."
It is understood that McLaren has been told it will get an answer from Vettel and Alonso very soon, and it wants to sort out its 2015 driver plans before the final flyaway races that begin with the Singapore Grand Prix next month.
Boullier refused to elaborate on the exact timing of a decision, but made clear it would not wait until the winter before knowing its 2015 line-up.
"It will be soon, a few weeks," he said.
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