Mercedes has told its customer teams that it will be unable to provide them with its updated engine this season.
The German car manufacturer elected to use all its remaining engine development tokens at the Italian Grand Prix to deliver an upgraded engine for works drivers Lewis Hamilton and Nico Rosberg.
The power unit utilised new fuel concepts that were introduced with a view to a 2016 development path.
Williams, Force India and Lotus had hoped to be able to get hold of the upgraded power unit towards the end of this season, in a bid to help their constructors' championship prospects.
But after evaluating the engineering demands of producing the parts, and eager to ensure that all its customers were treated equally, Mercedes has come to the conclusion that it cannot deliver enough components for the teams.
It means that the fourth engines of the season that most of its drivers are using this weekend are the old specification, meaning only the Mercedes works outfit will have the updated specification this year.
Sergio Perez said that Force India was not too disappointed at not being able to get the upgraded engines.
"At the moment all we have heard is that they are checking reliability to see if it is working well," he said.
"We are not planning to get any of the full spec for the rest of the year – but hopefully for next year we will.
"What we have heard from Mercedes is that it is not that big a step forward, so the team is not too concerned about not getting the engine."