ExxonMobil CEO Rex Tillerson has argued against sanctions the US and European allies imposed on Russia after it annexed the Crimean Peninsula.
State Department environmental report is facing increased scrutiny from allies within the Obama administration.
Involvement of some staff with other, unrelated TransCanada work fully disclosed.
A group of Republicans, Democrats, labour and business leaders and a Canadian ambassador are pushing for a quick approval.
Keystone XL has become a flashpoint for US environmentalists, who have branded it a symbol of “dirty oil”.
Says State assessment included “insufficient information” on environmental issues.