Perez signed a new contract some weeks ago but the sponsorship deals that go hand in hand with it have not yet been finalised.

"The key thing is is that the driver contracts are in place, and with Checo there are some quite sophisticated commercial agreements," Fernley told Motorsport.com.

"Those have got to be completed, and you can only do that once you've got the driver contracts, you can't do it the other way around. So discussions are ongoing.

"I don't see any reason why it won't conclude in a way that Checo stays with us, and hopefully the partners also stay with us.

"Commercial deals are commercial deals, and each person has got to do the best they can in those arrangements. It is quite sophisticated with Checo, and there are a number of sponsors who are linked in with the Mexican programme, so it takes time.

"Those people, or certainly a few of them, have been very tied up with the Olympics, so there have been no discussions over the last few weeks. I suspect it will be tied up in September."

Fernley says that the team is not disappointed with the fact that Perez had been so vocal in the media about the possibility of leaving.

"We don't take any offence with anything. It's a commercial negotiation, and all commercial negotiations are positioning, It's quite right and proper that he wants to do the best he can, and so do we.

"Those things take time and it will come out in the wash."

Fernley insists that the team does not have a Plan B in place should Perez leave.

"I think it would be totally inappropriate. We have a contract with Checo, and it would be completely wrong for us to be discussing anything with other drivers.

"I don't see a reason why the deal won't be done, so for me it's not something that we have to worry about at this stage. If and when that ever comes up, we'll look at it, but I doubt very much that we'll be doing anything other than having Nico and Checo in the car."