Two teams currently being supplied by Renault could be poised to quit the roster due to the high cost of next year's new V6 engines.

The French manufacturer has been widely reported as charging the most for a supply of its 1.6-litre turbocharged units, with Mercedes and Ferrari considerably cheaper, particularly for the smaller teams, and Germany's Auto Motor und Sport claims that Williams may have already agreed a switch to Mercedes, with Caterham also considering part ways with the regie in search of a more attractive cost alternative.

Williams' return to Renault power at the start of 2012 was hailed as the reunion of two great F1 powers that once yielded world titles but, aside from a spike in performance and a victory in Spain last year, the partnership has not produced anything approaching that form since. With Toro Rosso apparently close to a deal to join sister team Red Bull under the Renault awning, Williams could have the ideal opportunity to jump ship, with reports linking it to a Mercedes supply that is anything up to EUR5m a year less than it would have to pay the French concern.

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"Williams could change because its contract is up," Auto Motor und Sport correspondent Michael Schmidt suggested, before rumouring that Caterham was also considering a switch to a more cost-effective supply.

Should Williams complete the rumoured move to Mercedes, the German company would have four teams on its books for 2014 - with the works outfit, McLaren and Force India already on board - but with McLaren due to move to Honda power from 2015, there could be room at the inn for another customer.

Caterham could also consider Ferrari, which is likely to add back-of-the-field rival Marussia to its books next season as it looks to replace Toro Rosso on its client list, although there is the drawback of it having agreed terms to relaunch the Renault-owned Alpine sportscar brand.

Renault ambassador Alain Prost confirmed that talks regarding the regie's roster were taking place in Monaco, with a line-up hopefully to be agreed before too long.

"I'm not myself negotiating with the teams, but we all know that it's going to be accelerating during this weekend," he acknowledged, "I cannot say all the dates for all the teams, but I hope [things are sorted] very quickly."

The three-time world champion admitted that the cost of the new engine was a concern for everyone, but insisted that what the teams were being asked to contribute was only a fraction of Renault Sport's outlay on the programme.

"It is a problem, but it's all part of negotiation and the price you've said is much higher than it is in reality," he told reporters in Monaco, "Also, you need to know that the budget of Renault Sport F1 is EUR150m per year, and you can imagine, if you just make a very quick calculation about the price divided by four teams, for example, you will realise that Renault is paying a big contribution."