White House Economic Adviser Larry Kudlow said the next phase of U.S. tax reform will not happen during the final months of 2018, the "lame duck" period when Republicans will still control Congress.

A follow-up to Republicans' 2017 tax overhaul could be passed in the new session of Congress starting in January, Kudlow said, even though Democrats will hold the majority in the House of Representatives, the chamber that writes revenue and spending legislation.

Many changes were being considered "to make the code more efficient and more pro growth, ... flatter rates for everybody, particularly middle class people, get rid of the loopholes," Kudlow said to reporters at the White House.

"None of this I think will happen" with the current Congress, he added. "I don't see it."

When a reporter asked about Democrats' control of the House, Kudlow said: "That doesn't mean we couldn't get something in the new session."

President Donald Trump said last month his administration was planning to roll out plans for a 10 percent tax cut for middle-income people before the Nov. 6 congressional elections.