An anti-Keystone XL pipeline crusader has written to Prime Minister Stephen Harper, suggesting Canada's aggressive lobbying for the project played a part in the government shutdown south of the border.

Tom Steyer, a San Francisco billionaire and a major Democratic Party fundraiser, chastises Harper for saying he would not "take no for an answer" from U.S. President Barack Obama on TransCanada's Keystone XL.

In a question-and-answer session with the Canadian American Business Council last week in New York, Harper took a hard line on how Canada would respond if the Keystone XL project is rejected by the White House.

'This won't be final until it's approved and we will keep pushing forward.'- Prime Minister Stephen Harper

"My view is you don't take no for an answer," Harper said. "This won't be final until it's approved and we will keep pushing forward."

Steyer takes issue with those comments in his letter to the prime minister.

"Have your government, your government's lobbyist and/or agents representing TransCanada communicated with House Republicans about including Keystone in the original litany of demands put to President Obama?" Steyer asks in the letter to Harper sent Friday.

Steyer says in the dispatch that TransCanada is launching a new advertising campaign aimed at stakeholders in Washington, D.C.

"News of this advertising campaign comes in the context of House Republicans having closed down the U.S. government as well as threatening to oppose the extension of the country's debt limit unless certain demands were met," Steyer wrote.

"Included in the original list of House Republican demands was that the Obama administration grant approval for the building of the Keystone XL pipeline."

The combination of the advertising campaign and Harper's comments last week "raises the question of whether your office is working hand-in-hand with TransCanada to try to exploit the current situation in Washington, D.C., at the expense of the American people," Steyer wrote.