President Donald Trump on Monday dismissed the possibility of curbing a popular tax-deferred U.S. retirement savings program to help pay for sweeping tax cuts, and expressed doubts about adding another top bracket targeting the wealthiest Americans.

The potential scaling back of the 401(k) plans, which for four decades have helped Americans save for retirement, is one of several important details yet to be worked out in a major tax overhaul that Trump promised as a candidate and wants his fellow Republicans who control Congress to pass by year's end.

The White House and its allies in Congress have floated the idea of paring back a number of tax deductions to generate revenue lost as a result of their proposed tax cuts, the centerpiece of which is a sharp reduction in the corporate income tax rate.