(Adds detail bills, work ahead)
WASHINGTON, Dec 22 (Reuters) - U.S. President Donald Trump said he will sign Republicans' massive $1.5 trillion tax overhaul into law on Friday to cement the first major legislative win of his first year in office.
In a post on Twitter, Trump said he would finalize the tax plan, along with a short-term government spending bill that includes funds for missile defense, before departing for his Mar-a-Lago resort in Florida for the Christmas holiday.
The two pieces of legislation represent Trump's biggest accomplishment with Congress since taking office in January, as well as a sign of what awaits when he returns to Washington after Christmas.
The spending bill averts a partial government shutdown by extending federal funding through Jan. 19, largely at current levels. It does nothing to resolve broader disputes over immigration, healthcare and military spending.
Republicans also are divided over whether to follow up their sweeping overhaul of the U.S. tax code with a dramatic restructuring of federal benefit programs.
House Speaker Paul Ryan has said he would like to revamp welfare and health programs but Senate Republican Leader Mitch McConnell told National Public Radio on Monday that he was not interested in cutting those programs without Democratic support. (Reporting by Susan Heavey and Andy Sullivan; Editing by Bill Trott)