President Donald Trump said on Wednesday the United States was considering a big "fine" as part of a probe into China's alleged theft of intellectual property, the clearest indication yet that his administration will take retaliatory trade action against China.

In an interview with Reuters, Trump and his economic adviser Gary Cohn said China had forced U.S. companies to transfer their intellectual property to China as a cost of doing business there.

The United States has started a trade investigation into the issue, and Cohn said the United States Trade Representative would be making recommendations about it soon.

"We have a very big intellectual property potential fine going, which is going to come out soon," Trump said in the interview.

While Trump did not specify what he meant by a "fine" against China, the 1974 trade law that authorized an investigation into China's alleged theft of U.S. intellectual property allows him to impose retaliatory tariffs on Chinese goods or other trade sanctions until China changes its policies.