The diluted form of heavy crude from Canadian oil sands fields is no more likely to leak from a pipeline than other forms of oil, an arm of the National Academy of Sciences reported Tuesday.

The finding, after an extensive study by the National Research Council, refutes a claim by opponents of the controversial Keystone XL pipeline extension, who contend that the “diluted bitumen” it would carry is more corrosive than other forms of crude and thus more likely to leak.

The TransCanada pipeline company hopes to transport 830,000 barrels of crude per day from oil sands fields in Alberta to refineries in the Gulf of Mexico via the 1,100-mile Keystone extension. The project has become a litmus test for environmentalists, who say construction of the pipeline will promote more-rapid extraction of an especially dirty form of crude and contribute 15 percent more greenhouse gases than production of other crude oil. The State Department must decide whether to allow the project.

President Obama will lay out his agenda for addressing climate change in a speech at Georgetown University on Tuesday afternoon. He is not expected to discuss the pipeline.

The research council committee found no “evidence of chemical or physical properties of diluted bitumen that are outside the range of other crude oils or any other aspect of its transportation by transmission pipeline that would make diluted bitumen more likely than other crude oils to cause releases.”

It noted that diluted bitumen has been imported from western Canada for more than 30 years and flows through pipelines in the United States.

The committee was not asked to determine whether a leak of diluted bitumen would cause more damage to surrounding communities than a leak of other forms of crude.

Bitumen is a thick crude oil with the consistency of molasses. It must be diluted with other petroleum products to be transported via pipeline.

The American Petroleum Institute welcomed the report. Director Peter Lidiak released a statement saying that “since the U.S. Office of Pipeline Safety began keeping detailed statistics in 2002, not a single corrosion-related pipeline release from pipelines carrying any Canadian crude has been reported.” He cited a Canadian study that concluded that acid and sulfur compounds in oil sands crude are too stable to be corrosive.

But Jane Kleeb, head of BOLD Nebraska, one of the leading opponents of the pipeline extension, criticized the panel for failing to study the consequences of a diluted bitumen leak.

“Moms in Michigan and Arkansas [the sites of previous pipeline leaks] want this basic question answered: When a diluted bitumen pipeline spills, what are the health and economic risks to our families, land and water? The NAS failed them and our kids by not conducting an in-depth study of tar sands and diluents, including benzene, spilling in our water and near our homes.”