Trump said during the trophy ceremony for the Irish Open that he had been asked about the issue by everyone, including some of the golfers.
He told the crowd he had discussed whiskey tariffs with Irish Taoiseach, or prime minister, Micheál Martin and with tournament winner Shane Lowry.
"Everybody's been bugging me" to do it, Trump said.
"And I said, 'On behalf of the United States of America, I am going to take the tariffs off'," from Irish whiskey.
Irish whiskey currently faces the 15 per cent tariff imposed by Trump on imports from the European Union.
Trump announced in May that he was lifting certain tariffs on whiskey from the United Kingdom, which includes Scotch and spirits made in Northern Ireland.
Trump's apparent surprise announcement at the conclusion of the tournament was met with loud whistling and cheers from the crowd of spectators.
In May, the Irish Whiskey Association called for the tariffs to be removed, arguing that such a step would help many US companies with Irish products in their portfolios and avoid uncertainty for consumers.
Details on how soon the tariff would be lifted were not immediately available.
Trump said on April 30 that he gave the UK a tariff break on whiskey after King Charles III and Queen Camilla visited the White House.
"The King and Queen got me to do something that nobody else was able to do, without hardly even asking!" Trump posted on social media.
The Scotch Whisky Association said on July 24 that the zero-tariff policy had come into effect.
Trump on Sunday evening departed Shannon Airport aboard Air Force One, bringing an end to his two-day visit to Ireland.
with AP and PA
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