Some of the world's top auto-parts suppliers are not buying into all the enthusiasm about the electric vehicles hyped by Tesla's Elon Musk and larger carmakers trying to keep up.

Executives at five of the 25 biggest suppliers to carmakers in North America have downplayed this month's expectations for electric-vehicle sales.

After Volvo Car Group made a splash with its pledge to put electric motors in every new car by 2019 and Musk predicted more than half of United States car production would be electric in 10 years, the parts makers have issued modest forecasts and spoken in circumspect, even defiant, tones.

"There's a lot of buzz and a lot of talk about how the world's going to change to electrified vehicles overnight and I'm here to tell you it's not going to happen overnight, and it's not going to happen for decades," Mr David Dauch, chief executive officer of American Axle & Manufacturing Holdings, said on Tuesday at a JPMorgan conference in New York.

"I'm a strong believer in the internal combustion engine. I think it's going to continue to be here for some time."

The parts makers have to walk a fine line. Consumers have not yet demonstrated a willingness to buy electric vehicles in droves, giving carmakers and their suppliers reason to be conservative.

At the same time, governments are beginning to demand cleaner cars to curb pollution in mega cities from Mumbai to Mexico City. And investors seem inclined to reward those trying to transform transportation, with all-electric Tesla surpassing the likes of Ford Motor and General Motors by market value this year.

"Right now, you have an industry that's sort of stuck between the market and what they see from their clients," said Mr Matt Stover, an analyst with Susquehanna International Group in Boston. "They see Tesla with an enterprise value of US$70 billion (S$95 billion), and they see what their clients are awarding to them, and they say, 'Wow, something doesn't make sense here.'"

Magna International, the top parts supplier in North America by sales, sees pure electric cars being between 3 and 6 per cent of global new vehicle deliveries by 2025.

Chief executive officer Don Walker told an industry conference last week that carmakers share his scepticism of faster market penetration, but cannot say so publicly.

"They know what's going to happen, but they have to say what is going to be popular to be perceived as a progressive company," Mr Walker said on Aug 2 at the Center for Automotive Research Management Briefing Seminars near Traverse City, Michigan.

Magna and Delphi Automotive, which supply powertrains and electronics systems, see the way forward being paved with lots of hybrid engines.

Delphi CEO Kevin Clark told investors at the JPMorgan conference that 95 per cent of vehicles will still have combustion engines in 2025 and about 30 per cent will have some form of petrol-electric system. Just 5 per cent will be purely electric, he projected.

Price is one deterrent. Battery- electric sport utility vehicles (SUV) in the US will not reach price parity with traditional petrol engine-powered SUVs until 2026, Bloomberg New Energy Finance estimated in its Long-Term Electric Vehicle Outlook. For small cars, price parity will take until 2027 - and longer still in Europe.

BorgWarner, which has made two acquisitions in as many years worth about US$1.3 billion to help develop products for electric powertrains, forecasts that a fifth of vehicles will be hybrid or electric in 2023, with pure electric vehicles being just 3 per cent of sales.

Mr James Verrier, CEO of the maker of turbochargers, is sceptical of Musk's prediction to state governors last month that more than half of US production will be electric in a decade.

"I would probably say that too if I ran an electric vehicle company," he said in an interview on Monday in New York. "We hold a view probably similar to Magna that there will be an evolution towards a range of electrification."

The parts manufacturers are not in complete denial. As Musk prepares to unveil a battery-powered semi-truck this fall, suppliers to commercial vehicle manufacturers have been spending on electrification too.

"They have to defend their product mix, but they're probably being more active than they try to come across as," said Mr Kent Lucas, head of business development at VectoIQ, which connects suppliers and start- ups in the automotive space.

Dana Inc is investing in new parts for cleaner-running semi-trucks and construction equipment, though the company forecasts it will be at least a decade before commercial vehicles go electric. One contract the company has so far is to provide an axle for a battery-powered bus in China.

"We think our major programmes are not likely to be electrified within the next decade," Dana chief financial officer Jonathan Collins said at the JPMorgan conference. "We continue to have conviction around that, but investing now from a position of strength is a better position to be in."

BLOOMBERG