President Trump on Monday said he plans to introduce a proposal in the coming weeks for a reciprocal tax on imports, fulfilling a promise he made early on in his presidential campaign.

"We cannot continue to be taken advantage of by other countries," the president told attendees during a White House event on infrastructure. "We cannot continue to let people come into our country and rob us blind and charge us tremendous tariffs and taxes and we charge them nothing."

"We're going to be doing very much a reciprocal tax and you'll be hearing about that during the week and during the coming months," he said.

Commerce Secretary Wilbur Ross, who was also present for the event, endorsed the president's proposal and said the U.S. could benefit from a reciprocal tax because "we really have to claw it back" from other countries.

During his White House bid, Trump regularly threatened to implement a tax on imports from countries like Mexico and China to combat unfair trade practices. Under World Trade Organization and NAFTA rules, countries can impose tariffs for those reasons, but the rules also require tariffs to stay below committed levels, even if some countries' tariffs are allowed to be higher than others.

"When you say I'm going to charge a 10 percent or 20 percent border tax, everyone goes crazy, because they like free trade," the president told Fox Business last April.

"But when you sat 'reciprocal tax,' nobody can get angry," he added, describing his proposal as "whatever you charge, we're charging."