This story was updated at 3:18 p.m. EST.

As pressure mounts from both sides ahead of President Obama's crucial decision on whether to approve a controversial international oil pipeline, activists are taking direct aim at the two largest pipeline companies in Canada.

A new report released today by the National Wildlife Federation accuses TransCanada Corp. -- which is behind the proposed Alberta-to-Texas Keystone XL pipeline -- of abusing eminent domain powers, not properly consulting with American Indian tribes and obscuring its safety record. The report also takes aim at Enbridge Inc., which operated the pipeline that burst in Kalamazoo, Mich., in 2010 and has a variety of other lines transmitting oil from Alberta's oil sands.

The report comes as NWF and other groups continue to urge Obama to block construction of the Keystone pipeline, which they say would devastate the climate because of high greenhouse gas emissions generated through extraction of the oil sands crude it would carry as well as local environmental concerns in Nebraska.

A TransCanada spokesman, Shawn Howard, said the report was little more than a rehash of the same arguments pipeline opponents have long been making, and he stressed that the company complies with all of its legal requirements when dealing with landowners and others affected by a pipeline.

"This isn't a report. This is basically a brochure that has a series of stories in it that this same group of activists and lawyers put out," Howard said. "It's about their desire to end consumption of fossil fuels; it's got nothing to do with our pipeline."

Obama is expected to decide whether to approve the pipeline around the end of March 2013 -- a decision that environmentalists and industry both say will provide insight into his plans for a second term.

"Clearly Keystone doesn't fit in with creating a legacy on climate," said Joe Mendelson, NWF's director of climate and energy policy.