UPDATE 3-Fiat and Mazda join to make new Alfa Spider, MX-5
* New cars to be based on Mazda rear-wheel drive platform
* To be built at Mazda's factory in Hiroshima, Japan
* Both companies play down possibility of equity alliance
* Spider will be made from 2015, will be styled by Alfa
* Mazda shares close up 0.9 pct; Fiat down 1.3 percent
By Chang-Ran Kim and Jennifer Clark
TOKYO/MILAN, May 23 (Reuters) - Mazda Motor Corp and Fiat SpA will join forces to make new versions of their most famous sports cars, the MX-5 and the Alfa Romeo Spider, helping the two companies cut costs and possibly paving the way for a deeper alliance.
A joint venture announced on Wednesday will not include any equity tie-up but joins a long line of partnerships which carmakers have forged, aiming to share research and development costs and keep prices competitive in a tough market.
"I think this project itself is only the beginning. It opens a channel of communication between two companies that have never worked together" said UBS auto analyst Tatsuo Yoshida. "They said today that they're going to explore cooperation in Europe, but there's always scope for more, including the United States, for example."
The new cars will be based on a Mazda rear-wheel drive platform and will be built at Mazda's factory in Hiroshima, Japan.
The Alfa Spider, famed for its starring role in 1967 movie The Graduate, will be made from 2015 and will be styled separately by the Italian company, so the engine and look will be Alfa Romeo rather than Mazda.
Alfa Romeo pulled out of the United States in 1995 and is already set to return in late 2013 with the planned 4C sportscar.
Some analysts expect the revamped Spider to boost Alfa in the world's biggest two-seater sports car market and saw sales of around 20,000 a year.
"Over time, if you do a decent job of sharing platforms and engines, you can gradually grow scale," said analyst Philippe Houchois at UBS. "The accord with Mazda shows that Fiat, among Europe's three weakest car makers, is the one with the clearest plan for going forward."
Fiat has already built the small 500 in a joint venture with Ford Motor Co's Ka; the Fiat Punto with the Opel Corsa; and the Fiat Seidici with a Suzuki Motor Corp mini-SUV, sharing the investment costs of around 1 billion euros ($1.3 billion) needed to develop each new car.
Mazda's MX-5, launched in 1989, is the best-selling two-seat convertible sports car in history, with more than 900,000 sold, according to the Guinness Book of World Records in 2011.
But Japan's fifth-largest car maker is looking lonely on the global car alliance scene.
Ford owned a third of Mazda's shares under a 31-year alliance, but had to sell most of its stake to raise cash and now owns just 2 percent, leaving the Japanese company to link up with several rivals in joint ventures.
Cost savings from such deals have not been enough to save Mazda from posting four years of losses, as it struggles with a strong yen, which makes its cars less competitive overseas.
It builds most of its cars in Japan and exports almost 80 percent of them.
Analysts said the Fiat deal was not a panacea but was still positive news.
Mazda shares initially jumped 4.7 percent on reports of a tie-up, but fell back to close up 0.9 percent. Fiat shares were down 1.3 percent, outperforming a 3 percent drop in Italian stocks as a whole.
"Developing the next (MX-5) iteration for Mazda alone would have been difficult to justify, and this arrangement allows them to do that," said Yoshida.
The Italian group already owns 58.5 percent of Chrysler and wants to buy the rest. It is expected to complete its global footprint by adding an Asian partner at some stage, despite a troubled history with former Chinese partners. In India it has a manufacturing deal with Tata Motors.
Both Mazda and Fiat played down the possibility of an equity alliance, saying their non-binding memorandum of understanding did not involve such talks.
The companies will, however, discuss opportunities to cooperate in Europe, they said in a statement. Mazda sold 128,238 cars in the shrinking European market last year, around the same volume as Alfa Romeo. Fiat-Chrysler sold 928,390.
A final agreement between the companies is expected to be signed in the second half of this year.
Yoshida noted Mazda could make a new car in one of Fiat's factories in Europe.