US Senate Republicans passed landmark tax reform early Saturday, a critical step toward delivering a monumental legislative victory for President Donald Trump in his first year in office. 

After a marathon session, the chamber voted 51 to 49 in favor of the nation's largest tax overhaul in 31 years, overcoming stubborn internal Republican resistance and dismissing Democrats angry over the last-minute, handwritten changes to the legislation.

The Senate version and one passed earlier this month by the House of Representatives must now be reconciled into a single bill, and approved again by both chambers before it makes it to the president's desk for his signature.