The Republican-controlled U.S. Congress appeared all but certain to pass sweeping tax legislation this week after two Senate Republican holdouts agreed on Monday to support a tax overhaul backed by President Donald Trump.

As the Republicans' self-imposed Friday voting deadline loomed, Sens. Susan Collins and Mike Lee each said they had decided to back the legislation hammered out last week among Republicans from the Senate and House of Representatives.

"The first major overhaul of our tax code since 1986, this legislation will provide tax relief to working families, encourage the creation of jobs right here in America and spur economic growth that will benefit all Americans," Collins said on the floor of the Senate while announcing her support.