Renault has revealed that its Formula 1 recovery could be compromised by late payments from some of its teams.
The French car manufacturer put in to place an emergency action plan after a disastrous opening pre-season test to help it make up lost ground.
Those efforts have paid off so far, with Red Bull having emerged as a threat to Mercedes in the opening races.
Some of the funding for that plan was delivered by the Renault car company, but part of it is also reliant on payments from customer teams.
Renault's F1 president Jean-Michel Jalinier said ahead of the Spanish Grand Prix that he was unhappy that the project was being affected by unidentified teams not keeping up with payments.
"In order to develop the action plan we need to secure resources and our resources are coming from two sources," he said.
"One is Renault, and we have been able to secure the right resources, even human resources or financial resources, and the other part of it is coming from the teams because we are selling the engines to the teams.
"On this part I must say that we are not at an acceptable situation because some of the teams are just late in payments, and at the time you need to spend resources to catch up you cannot afford to have those [late] payments."
Jalinier declined to identify the teams who had not paid - but it would be unlikely to be Red Bull or Toro Rosso who are heavily backed by their energy drink company owners.
ENGINE SUPPLY DEALS COULD BE STOPPED
Renault says the situation is now critical, with matters needing to be sorted in a matter of weeks.
"It is a serious concern," Jalinier said. "We can live with it up to a certain point, because we are developing, putting money in the business, and we need to get our resources."
When asked whether or not it was possible for the supply deals to be cut if payments were not made, Jalinier said: "That is an option.
"You first need to work with your team in order to recover and get back to some kind of financial situation.
"We will have to address the situation with the teams and take decisions, because that is something that we cannot carry forward."