TransCanada has since reapplied for a presidential permit, putting the decision back in the State Department's hands and raising greens' concerns that Tillerson could fast-track the project. Then-President Obama - on advice from his State Department, led by John KerryJohn KerryState Dept: Tillerson has recused himself from Keystone decision Tapper: Tillerson traveling without press "insulting" Kerry signs memoir deal MORE - denied TransCanada's application in 2015, but Trump signed an order reopening the application process in January.
The file technically belongs to his office - the State Department decides whether to grant permits for pipelines that enter the US from overseas.
TransCanada quickly refiled an application to build its pipeline.
U.S Secretary of State Rex Tillerson has recused himself from State Department deliberations on granting a permit to TransCanada Corp.'s Keystone XL pipeline, heading off conflict-of-interest concerns over a project he praised when he was chief of Exxon Mobil Corp.
President Donald Trump in January ordered the secretary of state to "reach a final permitting determination" within 60 days of TransCanada's request, which came on February 10.
Should a special prosecutor be appointed to investigate Trump-Russia ties?
Independents are also divided, with 35 percent saying Russian Federation influenced the results, and 40 percent saying it didn't. But Trump won the White House by creating his own reality, built on what adviser Kellyanne Conway called "alternative facts".
The pipeline, which would bring oil from Canada to the US, was halted by then-President Barack Obama. It could carry 830,000 barrels of oil each day.
But Greenpeace launched a petition drive to ask the Office of Government Ethics to urge Secretary Tillerson to recuse himself from any decisions regarding the Keystone pipeline, as the former chief executive of the U.S. energy giant ExxonMobil has a conflict of interest in it.
It remains unclear whether Mr Tillerson still owns stock in ExxonMobil.
In State Department briefings earlier this week, acting spokesman Mark Toner said the secretary was "working with the Office of Government Ethics" on the issue.
Tillerson has to fully divest from Exxon by May as part of an agreement with the Office of Government Ethics.