A new television ad scheduled for broadcast on Sunday will call on President Obama to “do the right thing” to prevent climate change by rejecting the Keystone XL pipeline.

Produced and narrated by Tom Steyer, a billionaire hedge fund manager from California, the ad is the latest attempt by his political action committee to put pressure on Mr. Obama and try to counter proponents of the pipeline.

“Mr. President, you’ve had real accomplishments when it comes to fighting climate disruption,” Mr. Steyer says in the ad, which will run on broadcast television stations in Washington on Sunday and on cable networks across the country. “Let’s do the right thing on Keystone.”

The 1,700-mile pipeline would carry crude oil from the oil sands in Alberta, Canada, to American refineries on the Gulf Coast. Proponents say the project would create jobs and help the United States reduce its dependence on oil from the Middle East.

But opponents like Mr. Steyer say it will enable oil companies in Canada to extract and distribute much more oil from the ground and will contribute to the changing climate by pumping more carbon dioxide into the air.

Critics of the pipeline have one principal target: Mr. Obama. Because the pipeline would cross the border between the United States and Canada, it must get a permit from the State Department after environmental and other reviews. Mr. Obama has said he will make the decision about whether to approve the pipeline based in part on whether those reviews conclude that the pipeline contributes significantly to carbon pollution.

In the new television spot, Mr. Steyer claims that has already been answered.

“The truth? Scientists report Keystone oil would produce as much carbon pollution as 620,000 cars every year,” he says in the ad.