Red Bull motorsport advisor Helmut Marko has accused Ferrari of "playing games" as the two parties attempt to negotiate an engine-supply deal for 2016.
The Milton Keynes-based team are becoming increasingly desperate to find an engine supplier for next season, with their agreement with Renault set to be terminated and potential partnerships with Audi and Volkswagen not materialising.
Ferrari had said that they were open to supplying Red Bull with power units even though it would likely return the team to the front end of the field. However, according to motorsport.com, the Italian team have now said that they will only supply Red Bull with their 2015 power unit.
This has angered Marko who once again reiterated that Red Bull could leave Formula 1 as a result of their engine struggles.
"They are playing games with us," Marko told Auto Motor Und Sport. "But we don't want to play along.
"Our consideration to pull out is fuelled more and more.
"It is a cheek to offer us 2015-spec engines when, at the same time, Sauber and Haas F1 are going to get 2016-spec engines."
Marko's comments come after team principal Christian Horner admitted that his team's engine plans were now at a "critical" stage.
"The current situation is quite critical because, as we sit here, we don't have an engine," said Horner.
"We are already late, already very late. For Toro Rosso it is more critical than Red Bull. It was already difficult two weeks ago."