WASHINGTON (AP) — The Trump administration is studying the idea of implementing a big tax break for wealthy Americans by reducing the taxes levied on capital gains, but no decision has been made yet on whether to proceed.

Administration officials said Tuesday that Treasury Secretary Steven Mnuchin prefers deferring to Congress. But he does have his department studying the economic impact of such a change and the legality of proceeding without congressional approval.

The change would involve taxing capital gains — profits on investments such as stocks or real estate — after taking into account...