LONDON (Reuters) - Renault have warned Red Bull that they are running out of time to take up the French manufacturer's offer of a Formula One engine for next season and cannot wait until next month's Austrian Grand Prix.
Red Bull must decide between sticking with Renault, the manufacturer that powered them to four championships between 2010 and 2013 but with whom they fell out afterwards, and Honda who are now partners of Red Bull-owned Toro Rosso.
Red Bull team boss Christian Horner told reporters in Canada that the decision was likely to be made within two or three weeks.
"I think it will be after Paul Ricard (the French Grand Prix next week), around the Austrian Grand Prix I would suspect we'll be homing in on our position," he said.
The race at Spielberg is on July 1.
However, Renault F1 managing director Cyril Abiteboul said Austria was too late and that the deadline had already been extended once to allow Red Bull to compare the latest specification engines.
"I guess they have all the information that they need now. I don't see why they are going to further delay the decision," he told motorsport.com.
"Past a certain point, the offer we made, and that they requested, will not stand," the Frenchman added.
"It was Montreal that they wanted to wait for: our new spec, Honda's new spec.
"We will not be able to wait for the sort of timing that they've mentioned this weekend."
Red Bull's engines are already branded as Tag Heuer following the falling out but Abiteboul said at the weekend he hoped the two sides would stay together for a few more years.
He suggested that, if they did, Red Bull could become champions again. But he emphasised that his patience had limits.
"I have a date, they know the day, but we are not talking about Austria. Austria, we won't be here, and they will be talking directly to Honda," he said.
The engine decision has added importance for Red Bull with Australian Daniel Ricciardo out of contract at the end of the season and weighing up his options after winning two of seven races this year.
Honda, whose engine was once dominant in the 1980s, had a dismal three years with McLaren but have looked more competitive with Toro Rosso.
Whatever engine Red Bull go for is likely to be only a short-term decision, with the rules set to change after 2020.
(Reporting by Alan Baldwin; Editing by John O'Brien)