Foreign Affairs Minister Simon Coveney has criticised Donald Trump after the US president said he is freezing payments to the World Health Organisation pending a review of its warnings about coronavirus and China.
The US president said the Covid-19 outbreak could have been contained at its source with lives spared had the UN health agency done a better job investigating reports coming out of China.
The United States contributed nearly $900m (€823m) to the WHO's budget for 2018-19, according to information on the agency's website.
Mr Coveney tweeted that Mr Trump withholding funding was an "indefensible decision" in the midst of a pandemic.
"So many vulnerable populations rely on WHO - deliberately undermining funding and trust now is shocking," he wrote.
"Now is a time for global leadership and unity to save lives, not division and blame."
The United States is the biggest overall donor to the WHO, contributing more than $400m in 2019, roughly 15pc of its budget.
Some 1.99 million people globally have been infected and nearly 128,000 have died since the disease emerged in China late last year, according to a Reuters tally.
UN Secretary-General Antonio Guterres said it was not the time to reduce resources for the WHO.
"Now is the time for unity and for the international community to work together in solidarity to stop this virus and its shattering consequences," he said in a statement.
China, which has won WHO praise for its actions to curb the virus's spread, yesterday urged the United States to fulfil its obligations to the WHO.
"This decision weakens the WHO's cap ability and harms international co-operation," Foreign Ministry spokesman Zhao Lijian said.
EU foreign policy chief Josep Borrell said on Twitter: "Deeply regret US decision to suspend funding to WHO.
"There is no reason justifying this move at a moment when their efforts are needed more than ever."
German Foreign Minister Heiko Maas said apportioning blame did not help.
"The virus knows no borders," he said in a tweet.
New Zealand Prime Minister Jacinda Ardern said the WHO was essential to tackling the pandemic.
"At a time like this when we need to be sharing information and we need to have advice we can rely on, the WHO has provided that," she said. "We will continue to support it."