Red Bull is running Tag Heuer - badged Renault engines in 2018 but is weighing up a possible switch to Honda power for 2019. Picture: RenaultSport F1

London - Renault has warned Red Bull that it is running out of time to take up its offer of Formula One engines for 2019 and cannot wait until July'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 it fell out afterwards, and Honda which is now supplying engines to Red Bull-owned Toro Rosso.

Red Bull team boss Christian Horner said at the Canadian Grand Prix in Montral Canada the decision would probably be made within two or three weeks.

"I think it will be after the French Grand Prix next week at Paul Ricard," he said. Around the Austrian Grand Prix I would suspect we'll be homing in on our position."

'Too late'

But Renault F1 managing director Cyril Abiteboul said the Austrian race on 1 July would be too late; 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," he told motorsport.com. "I don't see why they are going to further delay the decision. Past a certain point, the offer we made, and that they requested, will not stand. 

"They wanted to wait for Montreal: 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."

Patience has limits

Red Bull's engines are already branded as Tag Heuer following the spat but Abiteboul said at the weekend he hoped the two would stay together for a few more years. He suggested that, if they did, Red Bull could become champion again - but emphasised that his patience had limits.

"I have a date, they know the day, but we are not talking about Austria," he said. "Austria, we won't be here, and they will be talking directly to Honda."

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 so far in 2018.

Honda, whose engine was once dominant in the 1980s, had a dismal three years with McLaren but has looked more competitive with Toro Rosso. Whichever engine Red Bull goes for is likely to be only a short-term decision, with the rules set to change after 2020.