Buffett, whose company has a major stake in the railroad company BNSF, said he did not see the pipeline's construction as a major problem for rail firms. "It's not that big a competitor," he said.
The pipeline would carry heavy crude from Alberta's oil sands region to refiners on the U.S. Gulf Coast. Proponents say it will provide a secure supply of oil from a trusted ally and create high-paying construction jobs; opponents argue it will accelerate oil development that will worsen climate change and could lead to oil spills on sensitive habitat.
While the billionaire has supported several of Obama's policies, including raising taxes on the wealthy, Buffett is not a vocal proponent of addressing climate change. Coal shipments are a major source of revenue for rail firms, and many rail companies have lobbied actively against any limits on carbon emissions from power plants.
Separately on Saturday, Shultz -- who served under President Ronald Reagan and has worked closely with one of the pipeline's most prominent opponents, billionaire Tom Steyer -- said he supported the pipeline on national security grounds. In 2010 Steyer and Shultz worked together to defeat a proposition financed by Texas oil firms to reverse California’s law capping greenhouse gas emissions.
Shultz told an audience at the Vail Global Energy Forum that he backed the project because it would make America less dependent on crude shipped from the Middle East. “That’s oil that doesn’t go through the straits of Hormuz,” he said.
At the same time, Shultz urged the crowd to take steps now to curb climate change.
“Global warming is a reality today, and it’s going to become more so," he said. "We need to be paying attention. If we do not do what we can do, we are not doing right by future generations, let alone our own."
Also on Monday, the Democratic governor of Missouri, Jay Nixon, endorsed the pipeline.