NEW YORK (Reuters) -Pharmaceutical imports to the U.S. surged in March as drugmakers stocked up ahead of potential U.S. tariffs on their products, which have historically been exempt from such fees.

Total imports of pharmaceutical products exceeded $50 billion in the month - the equivalent of 20% of all pharmaceutical imports in 2024, according to data from a U.S. Commerce Department report on Tuesday.

Imports jumped in particular from Ireland, the top drug exporter to the U.S. The country had a larger trade surplus than China with the U.S. for the first time in March.

Imports of all goods from Ireland rose by about $15.5 billion from February, with drugs accounting for most of that.

"While we had known consumer goods accounted for the bulk of March's rise, we can now see pharmaceutical products were $20 billion higher - almost all of which were imported from Ireland," Matthew Martin, senior U.S. economist at Oxford Economics, wrote following the report.

President Donald Trump has been threatening to levy tariffs on pharmaceuticals as part of a trade policy he says will increase domestic manufacturing of medicines.

Last month, the Trump administration launched a probe into imports of pharmaceuticals ahead of possibly imposing tariffs on the grounds that extensive reliance on foreign production of medicine is a national security threat.

Trump said on Monday he would make an announcement on the tariffs in the next two weeks. He also issued an executive order aimed at easing the regulatory burden in the U.S. for producing drugs.

In recent months, drugmakers told Reuters they had taken the unusual step of sending more medicines by air to the U.S. Two of the biggest U.S. drugmakers said on recent investor calls that they had stepped up efforts to bring in inventory as part of their preparation for tariffs.

"As you can imagine, we have done everything that we have to do to make sure that we mitigate, so that includes inventory, of course, and many other things," Pfizer ( PFE ) CEO Albert Bourla said on a company conference call. He said the company was increasing that inventory each month to make sure "we are well positioned."

Merck's ( MRK ) primary exposure is through blockbuster cancer drug Keytruda, the world's biggest-selling prescription medicine, much of which is produced in Ireland. The company said last month it had moved enough inventory to the U.S. to protect it through year-end.

In addition to Ireland and other European Union countries, Oxford's Martin said the countries most at risk from the anticipated drug import levies include Singapore and Switzerland.