LONDON: Mercedes will wait until the New Year before making any announcement on a replacement for retired Formula One world champion Nico Rosberg, with Finland's Valtteri Bottas still the favourite.

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team spokesman said on Thursday that nothing was planned between now and Jan. 3 and there was no significance in the latter date either, other than it marking the end of the holidays.

Bottas has become the bookmakers' favourite but neither his Williams team nor Mercedes have confirmed any approach has been made.

Rosberg surprised both his team and the sport by announcing his retirement five days after winning the championship in Abu Dhabi at the end of November, leaving Mercedes in a difficult position.

The sport's dominant team, who have won both titles for the past three years in a row, have the most desirable seat on the grid up for grabs but a shortage of experienced contenders who are also available.

The likes of double world champion Fernando Alonso, at McLaren, and Ferrari's four times title-holder Sebastian Vettel have ruled themselves out.

"We have an agreement with McLaren and we are going to respect that," Alonso's manager Flavio Briatore told Italy's Gazzetta dello Sport last week.

Bottas, 27, is under contract to Mercedes-powered Williams but has had management ties to Mercedes team boss Toto Wolff since he entered the sport.

The BBC reported at the weekend that Wolff had offered Williams a 10 million euro (8.39 million pound) cut in their engine bill in return for allowing Bottas to leave, with that initial approach rejected but negotiations continuing.

Mercedes have German reserve driver Pascal Wehrlein, who raced for Manor this year, under contract and immediately available.

The fact that he has not been confirmed indicates that they are searching for someone with more experience to partner triple world champion Lewis Hamilton.

The sport's commercial supremo Bernie Ecclestone said this week that the sport needed Mercedes to get the strongest possible candidate to prevent Hamilton running away with a fourth championship.

"I don't think anybody is going to beat Lewis," he told Sky Sports television.

"Nobody would want to buy tickets and go to watch a race or watch on television Lewis disappearing from us when the lights go off, and probably lapping the field a couple of times.

"It would be bad for everybody and bad for Lewis as well, because I think he wants to win fair and wants to beat somebody."

(Reporting by Alan Baldwin, editing by Steve Keating.)