Republican senators started the new U.S. Congress on Tuesday with legislation to approve TransCanada Corp's pipeline from Canada to the United States and White House spokesman Josh Earnest said Obama would not sign it.

The White House's Office of Management and Budget on Wednesday issued a statement formalizing the veto threat.

The statement said the House bill would circumvent presidential authority and prevent thorough consideration of security, safety and environmental concerns.

(Reporting by Bill Trott; Editing by Marguerita Choy)