Baku, October 3, AZERTAC
Formula 1 boss Bernie Ecclestone is coming under pressure behind the scenes to pick Michelin rather than Pirelli as the sport's next tyre supplier, according to BBC.
Pirelli's deal began in 2011 but it is in competition with Michelin for the new contract that runs from 2017-19.
Several leading teams have expressed a preference for a change because of concerns about Pirelli after a series of problems.
Governing body the FIA is also said to have doubts about the Italian company.
The FIA had approved both bids on technical and sporting grounds, leaving the decision in the hands of Ecclestone, who puts together the commercial aspects of the deal.
But it has now has gone back to Pirelli with further questions following the company's reaction to two high-speed failures at last month's Belgian Grand Prix.