GEOFF BENNETT: Today, the Biden administration rolled out its most aggressive effort yet to combat climate change with tougher emissions limits for cars and trucks.

But a number of challenges remain, including in the cost of electric cars, the batteries and how to charge them on the road.

William Brangham has our report on the administration's latest move.

WILLIAM BRANGHAM: Cleaner cars, cleaner air as quickly as possible, that's the stated goal of the Environmental Protection Agency's new proposed emission standards for tailpipes.

If enacted, these standards could mean that, in less than 10 years, as many as two out of every three new vehicles sold in America would be all-electric.

It's the nation's most ambitious effort yet to cut the greenhouse gas emissions that are driving climate change.

The administration argues that this shift to zero-emission vehicles would help the U.S. meet its pledge to cut overall emissions in half by 2030.

EPA Administrator Michael Regan laid out the plan this morning.

MICHAEL REGAN, Environmental Protection Agency Administrator: This is historic news for our children.

It's historic news for our climate.

It's historic news for our future.

WILLIAM BRANGHAM: The EPA set forth two sets of proposed rules today, one governing cars and light trucks, the second for heavier vehicles like buses and trailer-trucks.

If enacted, the EPA says emissions from those small and medium vehicles would drop by 44 to 56 percent.

MICHAEL REGAN: As a father of a 9-year-old, I can assure you that there is no greater priority for me than protecting the health and well-being of our children, ensuring that they have a safe, healthy and reliable future.

WILLIAM BRANGHAM: Transportation is the largest source of America's greenhouse gas emissions, accounting for around 27 percent of the U.S.' carbon pollution.

Supporters say this move by the EPA is a welcome addition in the fight to curb the worst impacts of climate change.

FRED KRUPP, President, Environmental Defense Fund: It's a dream come true for those of us who know we need to decarbonize our society and certainly our cars and trucks.

WILLIAM BRANGHAM: Fred Krupp is president of the Environmental Defense Fund.

FRED KRUPP: EPA has the authority to reduce the amount of tailpipe pollution.

And when you reduce it enough, the way to meet that is through zero-emitting vehicles like electric cars.

And that's the mechanism.

If a company can do it with a hydrogen fuel cell or an electric vehicle, they're allowed to do that.

But, in reality, the electric vehicle is the answer that not only Tesla, but GM, Ford, Stellantis, have all chosen as the best way to clean up that tailpipe.

WILLIAM BRANGHAM: This shift would require automakers to dramatically ramp up production of electric vehicles.

Last year, E.V.s were roughly 5.8 percent of new cars sold in the U.S.

Right now, they are about 7 percent.

But EPA Administrator Regan said the industry is ready for this surge.

MICHAEL REGAN: Listen, over the last two years, over $120 billion of private sector investment in electric vehicles and batteries.

I believe it because when I look at the projections that many in the automobile industry have made, this is the future.

The consumer demand is there.

The markets are enabling it.

The technologies are enabling it.

WILLIAM BRANGHAM: The effort to transition to electric cars is already under way in this country.

And almost all automakers have rolled out new electric models, with a few even pledging to go fully carbon-neutral soon.

But, still, there are some real challenges ahead on the road to an all-electric future.

One is about the batteries for these cars.

The minerals currently needed for them, lithium, nickel, cobalt and others, are primarily produced in China, and some are mined in dangerous, inhumane conditions in parts of Africa.

But there are other issues.

John Bozzella is the president of the Alliance for Automotive Innovation, which represents carmakers.

JOHN BOZZELLA, President and CEO, Alliance for Automotive Innovation: When you talk to consumers, what you often hear is, how far will this go on a charge and where can I charge it?

And so that raises two immediate questions.

Do we have sufficient charging infrastructure?

Are there high-speed chargers available on interstates between metropolitan areas, so that I can take a longer trip, as opposed to just moving three or four miles around my hometown?

WILLIAM BRANGHAM: There are roughly 53,000 charging stations currently in the U.S., compared to triple that number of gas stations.

President Biden has pledged construction of new charging 500,000 stations nationwide by 2030 and set aside over $7 billion in the 2021 infrastructure law to pay for it.

FRED KRUPP: Charging stations are becoming increasingly ubiquitous.

In the last few days, 7/Eleven announced that they will have charging stations at all their locations.

You will be able to drink a Slurpee while you're charging your car.

And Walmart, which already has 1,300 charging stations, has announced they're going to build thousands more at every single Walmart and Sam's Club.

WILLIAM BRANGHAM: Another impediment is cost.

The current average E.V.

costs about $65,000.

That's roughly $17,000 more than the average gas-powered car.

Even with the federal tax credit of $7,500, which not all E.V.s qualify for, plus the longer-term savings of never having to buy gas, that initial sticker shock has kept some buyers away.

JOHN BOZZELLA: Right now, the average transaction price of electric vehicles is substantially higher than the average transaction price of an internal combustion engine vehicle.

Will that change over time?

Of course it will.

WILLIAM BRANGHAM: Because these EPA rules are an expansion of existing statutes, analysts believe they will likely be challenged in the courts.

For the "PBS NewsHour," I'm William Brangham.