Pirelli motorsport director Paul maker has admitted there are no guarantees that the Italian tire firm will bid to return for a second term as the World Rally Championship's control tire supplier.
Pirelli's three-year WRC deal comes to an end next season and, while Hembery says the company will consider the FIA's tender document for 2011 to 2013, a repeat of the 11 million euro investment in the current deal is highly unlikely.
"We'll sit down and look at the document," said Hembery, "but the world has changed significantly since the last time we made our proposal to the FIA.
"We will study the interest in the sport and gauge the effect of our current supply contract to the WRC. I can then present to the board of Pirelli, but it's not a given that we will get the nod from them.
"Don't forget, we've had to close factories, lay people off and sometimes the sport has to come second. This is purely a financial thing."
Hembery was at pains to point out that he firmly believed in the direction the WRC is now moving in.
"I like the way the sport's going," he added. "ISC as a global promoter is perfect, the events are working well and the calendar's coming to what we want. But if you want me to say that I'm happy to sit down and re-sign for another three years, well that's a board decision.
"We have stuck with the sport through what have been some pretty tough years, with low entry levels and manufacturers pulling. We've lived through those difficult times and we would want some assurances on the levels of manufacturer interest and assurances on the calendar front – on things like Monte Carlo returning."
Pirelli's investment in the sport has allowed the FIA to deliver the Pirelli Star Driver programme, which takes five drivers from the African, Asia-Pacific, European and Middle-East FIA Regional Championships and puts them in Group N cars for six rounds of the WRC. This year's program has helped uncover Finnish star Jarkko Nikara.
French tire firm Michelin is expected to tender for the WRC contract via its BFGoodrich brand, which is currently supplying teams in the Intercontinental Rally Challenge.