Political and business leaders gathering in San Francisco for a major climate change summit have committed to moving towards what was once a fantastical thought – the demise of the internal combustion engine in cars, trucks and other vehicles.

A group of 26 city, business and regional or state leaders, representing 122 million people around the world, have used the Global Climate Action Summit to call for carmakers to quicken the pace of electric vehicle rollout. Twelve cities, including Santa Monica, Tokyo and Greater Manchester, have pledged to deploy only zero emission buses from 2025.

This follows a move by 19 US cities and counties to increase the number of electric vehicles in their own fleets and promises by businesses such as Ikea, which plans to make its home deliveries emissions-free, to shift away from gasoline-powered cars and trucks.

“This demand added together really gives auto companies the message that they need to signal the endgame for the internal combustion engine,” said Helen Clarkson, chief executive of the Climate Group, which is behind the zero-emission vehicle challenge. “When you see cities making these sort of commitments, it creates a new normal in the market. Transport is a bit behind on the curve of the energy transformation but we are really seeing things move now.”

The electrification of transport is particularly challenging in the US, where transport is now the largest contributor of greenhouse gases, eclipsing energy, and drivers have opted for larger cars amid low fuel prices. The Trump administration is also in the process of weakening fuel efficiency standards that would push carmakers to expanding their electric vehicle fleets.

But mayors at the climate summit - convened by California’s governor, Jerry Brown, who has himself set a target of 5m electric vehicles on the state’s roads – have said they can look to bypass the federal government and help the US catch up to the likes of India, China and the Netherlands, which have all committed to phasing out carbon-polluting cars at some stage.

“The clean transportation revolution is now staring us in the face,” said Eric Garcetti, mayor of Los Angeles. Garcetti was one of 35 mayors of California cities to write to state regulators last month to demand 100% zero-emission buses by 2040. “Cities are where it is at. It’s more important who is in this house [in reference to San Francisco city hall, where he was speaking] than the White House. We need more zero-emissions cars, trash trucks, buses, whatever.”

Nearly 200,000 electric vehicles were sold in the US last year, although relative sales lag behind many other countries, with analysts blaming lack of marketing by large auto firms, cultural attachment to large cars and anxiety over driving range. It is expected that several US cities and states will use the climate summit to pledge an expansion of electric recharge points.

Erik Solheim, the UN’s environment chief, said that half of vehicles bought in his native Norway are now electric or hybrid due to a change to tax incentives and allowing electric vehicles to drive in dedicated bus lanes.

“With political leadership, it can change a lot faster than people think,” he said. “In Norway you see Nissan Leafs everywhere now. Every city and state should look to see what they can do on this.”

Elected officials in the US are not going as far as naming an end date for carbon-emitting vehicles, but advocates for electric vehicles hope even the more modest commitments will provide the momentum to radically change the face of car fleets, thereby helping avoid dangerous climate change and lessen the health impacts of air pollution near roads.

“Transportation for a long time has been the lost stepchild because everyone has focused on electricity,” said Sue Reid, vice-president of climate and energy at Ceres. “But we are now seeing electric vehicles becoming cost competitive right at the point of sale due to improvements in battery technology.

“There is a gap in awareness and education in the US but once that is bridged, things will change. This is the beginning of the end for the internal combustion engine. Soon, it won’t make sense for automakers to be producing cars on different platforms.”