Pakistan's Imran Khan calls for lifting of Iran sanctions
"I would stress and insist to the international community to lift the sanctions on Iran," Khan said at a press conference.
"It is very unjust they are dealing with such a large outbreak on one side, and on the other they are facing international sanctions."
Pakistan's foreign office did not provide any additional details on Rouhani's letter to Khan.
Iranian Foreign Minister Mohammad Javad Zarif took to Twitter on Tuesday to say that US sanctions were "impairing" Iran's ability to fight the COVID-19 disease.
Pakistan shares a 960-kilometre (600-mile) border with Iran, with the main crossing point located at Taftan in Balochistan province.
Pakistan sealed its border with Iran last week, but not before hundreds of pilgrims returned home from the Islamic Republic, which has been one of the countries worst affected by the coronavirus outbreak.
The US withdrew from a landmark nuclear deal and began reimposing punishing sanctions on Iran in 2018, blocking banking transactions and oil sales, among other sectors.
Read more: US sanctions on Iran put us all at risk during coronavirus
Tensions have soured further since the US assassination of Iranian commander Qasem Soleimani in January.
Pakistan offered to mediate between the US and Iran in a bid to defuse tensions following the killing.