By Jake Spring

TIANJIN, China (Reuters) - By 2020, Beijing says automakers must meet tough new green standards to cut epic pollution in China's cities. As domestic firms bet heavily on electric cars to meet that goal, foreign peers are set to stay in a different, petrol-driven gear.

In the latest sign of caution from global automakers in China, Germany's Audi last week unveiled a new factory for high-efficiency transmissions in Tianjin, to be used in petrol-powered cars. While Chinese firms go electric in the world's biggest auto market, Audi is intent on petrol engines that can run farther, cleaner, in tandem with hybrid technology.

As China's electrified vehicle production booms, some international industry officials warn in private that the ambitious electric goals of domestic firms could prove too costly, too risky, too far from what consumers actually want - and not a good fit with their operations elsewhere. Still, China doled out $4.5 billion last year alone in green car subsidies.

"In 2020, most cars we will sell will be combustion engines, so to fulfill (fuel consumption targets) you have to improve the consumption of each and every car of the Audi model range," Audi China chief Joachim Wedler said at the opening of the new plant. Wedler didn't comment on Chinese peers' electric car plans.

Automakers globally have struggled to agree on what a greener future will hold for the industry. In China, Beijing and state-linked automakers have thrown their weight behind electric vehicles - despite the fact that the electricity they need may be generated from burning coal.

Under Beijing's 2020 requirements, on average cars must consume less than 5 liters of petrol per 100 kilometers - nearly 30 percent below current standard levels.

Beijing has rolled out a raft of incentives to push domestic automakers - foreign brands generally aren't eligible - to build more electric and plug-in hybrid vehicles, spurring a quadrupling in sales of these so-called "new energy vehicles" (NEVs) in 2015. Even with that surge, just 1.4 percent of cars sold in the first seven months of 2016 were NEVs, as concerns linger over driving range and home charging.

HYBRID COMPROMISE

A powertrain manager at a major foreign automaker's China joint venture said domestic companies' smaller scale made them nimbler. Many are also state-linked, therefore obliged to support government policy, the manager said, declining to be named as he was not authorized to speak to the media.

For example, Geely - controlled by Li Shufu, a member of the government's political consultative body - wants 90 percent of all sales to be NEVs by 2020. Meanwhile, state-backed GAC Motor plans to be able to produce up to 400,000 green energy cars annually by the end of this year.

Foreign automakers, who must form joint ventures with local partners to produce cars in China, have to consider a different dynamic - how manufacturing strategies on the mainland correlate with their traditional businesses and customers elsewhere.

The powertrain manager said his company, like Audi, is focusing on a more gradual strategy, developing more efficient engines as well as plug-in petrol-electric hybrids: an interim solution that will please a government intent on cutting harmful emissions.

Of course, foreign automakers aren't avoiding NEVs entirely.

General Motors' China venture last year pledged to spend $4 billion on electrification, developing 10 new energy models by 2020.

In Tianjin, Audi China chief Wedler said the German firm and partner China FAW Group plan to launch their first locally produced plug-in hybrid vehicle this year, with a new imported car based on the same principle on the way next year.

But Wedler acknowledged that as China's massive auto market evolves, automakers alone won't determine future directions.

"The whole picture is driven by legislation," Wedler said.

($1 = 6.6791 Chinese yuan renminbi)

(Reporting by Jake Spring; Additional reporting by Shanghai newsroom; Editing by Kenneth Maxwell)