Exxon Mobil CEO Rex Tillerson said Friday that politics have thwarted the proposed Keystone XL pipeline that would bring oil-sands crude from Canada to Gulf Coast refineries.

“The unfortunate decision to halt progress on the pipeline was a product of political calculations in Washington,” Tillerson said at a major energy industry conference in Houston.

In January the Obama administration denied TransCanada Corp. a cross-border permit for the pipeline, a project that major business groups and several unions support but environmentalists bitterly oppose.

Tillerson urged continued pressure in favor of Keystone.