President Donald Trump ordered his administration to consider imposing reciprocal tariffs on numerous trading partners, raising the prospect of a wider campaign against a global system he complains is tilted against the U.S.

The president on Thursday signed a measure directing the U.S. Trade Representative and Commerce secretary to propose new levies on a country-by-country basis in an effort to rebalance trade relations — a sweeping process that could take weeks or months to complete. Howard Lutnick, Trump’s nominee to lead the Commerce Department, told reporters all studies should be complete by April 1 and that Trump could act immediately afterward.

Fresh import taxes would be customized for each country, meant to offset not just their own levies on U.S. goods, but also non-tariff barriers the nations impose in the form of unfair subsidies, regulations, value-added taxes, exchange rates, lax intellectual property protections, and other factors that act to limit U.S. trade, according to a copy of the memo distributed by the White House.