REGINA - Canada's ambassador to the United States says a controversial oil pipeline should go ahead and that arguments against the project have "fallen like a house of cards."

Gary Doer spoke to a lunch crowd in Regina on Thursday about the proposed TransCanada (TSX:TRP) Keystone XL pipeline. The $7 billion project would carry oilsands oil from Alberta to refineries on the Gulf Coast.

"If it's based on fact and reports and merit, it will happen. If it's based on noise, it won't," Doer said after his speech.

There has been a lot of noise about the 2,700-kilometre pipeline, which would also carry oil from the Williston Basin in western North Dakota and eastern Montana to downstream markets.

Advocates say it will create thousands of jobs and help end U.S. dependence on Middle East oil.

Opponents argue the pipeline would bring "dirty oil" that requires huge amounts of energy to extract and is an environmental disaster waiting to happen.

Doer told the Saskatchewan Trade and Export Partnership that concerns about emissions and water use in the oilsands are outdated.

"Some of the concerns about the oilsands, 15 years ago, those allegations were correct. The emissions were 80 per cent higher. They're now below California thermal oil," said Doer.

"Some of the concerns raised about water utilization ... about 10 barrels of water to one barrel of oil, those have gone down below, dare I say it, the amount of water required for ethanol. They have gone down and down and down."

"Some of the concerns have been dealt with and they've fallen like a house of cards with the State Department's latest environmental assessment."

The U.S. State Department said late last month that the pipeline poses no major risks to the environment.

Ottawa has already approved the Canadian portion of the pipeline and officials are lobbying hard for American approval. The State Department is expected to decide by the end of the year.

Meanwhile, hearings are being held this week in the six states the pipeline route would cross.

State regulators in North Dakota said Wednesday that they support the pipeline, though they want it built in a responsible manner.

South Dakota Gov. Dennis Daugaard said Thursday he supports the construction. Daugaard said he could not attend a hearing being held Thursday in Pierre by the U.S. State Department, but that an aide would deliver a letter from him urging federal officials to approve the project. Daugaard said the proposed pipeline will create jobs in South Dakota, provide more than US$10 million in local property taxes each year and provide a way to deliver oil produced in the state to refineries.

Ambassador Doer said there have been many other voices coming out on the pipeline.

"You've got veterans saying that we should get oil from Canada instead of risking lives in the Middle East. You've got a pipe worker saying just at a hearing that 'This pipeline is not just a pipeline to me, it's a lifeline.' "

With files from The Associated Press