The latest USA step comes amid Iran being rocked by violent protests sparked by the sudden decision to hike gas prices.
Protests erupted in Iran on Friday, hours after it was announced the price of petrol would rise to 15,000 rials a litre (12 USA cents) from 10,000 for the first 60 litres and to 30,000 rials for any extra fuel bought after that each month.
But the exact scale of the unrest remains unclear as authorities have curbed internet access to stop the use of social media to organise rallies and disseminate videos.
Iran's foreign ministry slammed US Secretary of State Mike Pompeo after he tweeted "the United States is with you" on Saturday in response to the demonstrations.
The waivers are one of the last remaining components of the 2015 nuclear deal the Trump administration withdrew from previous year.
"We condemn the lethal force and severe communications restrictions used against demonstrators".
A day earlier, Mr Pompeo had in a tweet said that the U.S. will be standing with people of Iran.
Mr Mousavi blasted Washington's "ill-intent" over its decision to reimpose sanctions on Tehran after the United States withdrawal in May a year ago from the landmark 2015 Iran nuclear deal.
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The step comes as Iran is rocked by violent protests sparked by sudden decision to hike gas prices.
Pompeo again voiced solidarity with the protesters, saying: "The world's watching".
Right after the price hike, President Hassan Rouhani said the government has no intention to receive any portion of the hike despite the economic woes in the country.
"I order the Planning and Budget Organisation to start from tomorrow to pay people the sum needed to be paid to them", he said, as quoted by his official website.
In an address on Sunday morning, Ayatollah Khamenei warned that the sporadic protests and acts of vandalism in Iran would create insecurity.
Frustration has grown over a sharp devaluation of Iran's rial currency as well as spikes in the prices of bread, rice and other staples since Washington began to apply "maximum pressure" on Iran to make tougher nuclear and security concessions.
More specifically, each individual project is unjustifiable and unsafe, in part because each gives Iran cover to keep facilities open and engage in illicit activities.
Fox News Radio's Guy Benson sat down for a radio exclusive with Morgan Ortagus, State department spokesperson who explained in further detail why Secretary Pompeo spoke up today.