Trump has accused the UN body of covering up the seriousness of the COVID-19 outbreak in China before it spread around the world.
The US president on Tuesday ordered that payments amounting to $400 million be halted pending a review of the WHO's role in allegedly "severely mismanaging and covering up the spread of the coronavirus".
The death toll from the COVID-19 pandemic has topped 125,000 around the world, with more than two million people infected by the disease since December.
Iran's Foreign Minister Mohammad Javad Zarif likened the funding freeze to the United States' "maximum pressure" campaign against his country.
The United States reimposed crippling sanctions against Iran in 2018 after Trump unilaterally withdrew from a nuclear deal.
"The shameful defunding of WHO amid a pandemic will live in infamy," Zarif wrote on Twitter.
"The world is learning what Iran has known & experienced all along," he said.
'Vainglorious blathering'
"US regime's bullying, threatening & vainglorious blathering isn't just an addiction: it kills people," added Zarif.
Iran itself is battling the Middle East's most deadly coronavirus outbreak and on Wednesday reported that another 1,512 people had tested positive for the COVID-19 illness.
It has repeatedly called on the Trump administration to reverse its sanctions policy, which has been opposed even by some US allies, particularly since the pandemic hit.
Medicines and medical equipment are technically exempt from the US sanctions but purchases are frequently blocked by the unwillingness of banks to process payments for fear of incurring heavy US penalties.
The new infections confirmed by Iran on Wednesday took the total number in the country to 76,389, Jahanpour said, noting that 49,933 of those hospitalised had recovered and been discharged.
The government of President Hassan Rouhani has struggled to contain the outbreak that emerged two months ago.
It shut schools and universities, postponed major events and imposed a range of other restrictions, but it has stopped short of ordering lockdowns.
Iran allowed small businesses outside Tehran to reopen on Saturday and is set to extend the measure to the capital next week.
The move has faced criticism from health experts and even some authorities.
Iran has requested a $5 billion emergency loan from the International Monetary Fund to battle the coronavirus outbreak.
But the United States, which effectively holds a veto at the IMF, has signalled it has no intention of agreeing to give Iran such a credit line, alleging that it would be used to fund "terror abroad".