UPDATE 1-Motorcycling-Rossi to rejoin Yamaha after leaving Ducati

(Adds details, quotes)

* Rossi to join Lorenzo at Yamaha

* Ducati finding partner for Nicky Hayden

ROME, Aug 10 (Reuters) - Italian motorcycling great Valentino Rossi will leave Ducati at the end of the MotoGP season and rejoin Yamaha on a two-year deal, the Japanese-owned team said on Friday.

"In June, we were able to sign Jorge Lorenzo for the 2013-14 campaign and now we are able to confirm Valentino Rossi for the next two years," Yamaha Motor Racing managing director Lin Jarvis said in a statement.

The 33-year-old nine-times world champion - seven in the premier class - first joined Yamaha in 2004 and won four MotoGP titles with the manufacturer before agreeing a two-year deal with Ducati at the end of the 2010 season.

However, the dream of pairing up Italy's best-known rider with Italy's top team turned into a nightmare and he finished seventh on an uncompetitive bike last year.

This season has been just as bad with Rossi lying eighth.

Rossi left Yamaha because he felt having two very strong riders in one team did not work. His then Yamaha team mate was 2010 champion and current championship leader Lorenzo but the Italian will now return to the same arrangement.

Spaniard Lorenzo has ridden for Yamaha since 2008 and leads the current championship by 23 points after 10 races of the 18-race season. Rossi has secured just one podium finish all season.

"We have run this 'super team' together in 2008, 2009 and 2010 and during that time we achieved the triple crown titles with Rider, Manufacturer and Team World Championship victories for three consecutive years," Jarvis said.

"I have no doubt that with the experience, knowledge, skills and speed of these two great champion riders we will be able to challenge for many race wins and for the 2013 and 2014 World Championship titles."

Ducati said they were in the process of finalising their 2013 championship lineup having recently renewed their agreement with American Nicky Hayden.

Rossi, who last won the championship in 2009, has often been linked with a move to Formula One team Ferrari and pundits wonder whether Rossi made an error in not switching to four wheels when he had the chance with the Italians in 2006 and again in 2009. (Reporting by Steve Scherer, Terry Daley and Amlan Chakraborty; Editing by John O'Brien/Mark Meadows)