Warning that the $7-billion Keystone XL pipeline constitutes "a huge attack on our climate," American actor Mark Ruffalo joined a Washington protest Sunday that planned to encircle the White House.

"If we're honest about climate change, we need to face this head-on," the Academy Award-winning actor said in an appearance on CTV's Question Period. "And exploiting the tarsands is not the way to do it."

Ruffalo, who has joined actors Darryl Hannah and Robert Redford in a stand against the pipeline, predicted there would be 10,000 people marching in a ring around the White House.

"We want to stop it," he said of the $7-billion project that will carry oil from Alberta to Texas. "This is a huge attack on our climate."

Ruffalo also said the economic benefits of the pipeline are suspect.

"The job numbers are wildly inflated," he said, noting that proponents of the project had cited 250,000 jobs created to start with but that number has declined to 6,000. "The only growing job sector is renewable energy."

With U.S. President Barack Obama within a couple of months of making a decision on the pipeline, Ruffalo said it is time for Obama to make good on his election promise that "this will be the generation to end the tyranny of oil."

"If he's not going to make those promises happen, we'll go on without him," the actor said, adding: "Change is in the air today."

In an interview from Calgary on Question Period, TransCanada Corp. CEO and president Russ Girling said the debate over the pipeline has been hijacked by celebrity protesters who have transformed it into a philosophical debate between the use of fossil fuels and alternative energies.

"The way they have introduced that debate is by using fear that if you let this project occur you will be introducing the biggest carbon bomb in the world and that couldn't be farther from the truth," he said.

"They have used celebrities to get that into the living room of the average American."

When asked about a possible change in the route, Girling said that would scuttle the pipeline by sending it back to square one. And he added that is unnecessary because environmental studies have shown the present pipeline plan has "no material impact on resources along the route."

He said the pipeline makes "infinite sense" and he warned that stopping the pipeline would increase greenhouse gas emissions because of all the tankers that would be needed to transport oil from Alberta to Texas.