The chief of the United Nations nuclear monitoring body and his team arrived in Tehran ahead of the country's plan for partly halting ocular inspections by the agency to its nuclear plants, the Associated Press reported Sunday, citing the state-run IRNA news agency.

Rafael Grossi, UN nuclear watchdog director, arrived late Saturday for a series of meetings on the eve of Iran's deadline for U.S. sanctions to be removed, as U.S. President Joe Biden called for "careful diplomacy".

Grossi was welcomed in Tehran by Kazem Gharibabadi, Iran's envoy to the IAEA, and Iran Atomic Energy Organization official Behrouz Kamalvandi, Gharibabadi said in a Twitter post on Saturday. The IAEA director's visit is set to run until Sunday.

Grossi will meet Iranian top nuclear officials including Ali Akbar Salehi, chief of the Islamic Republic's nuclear department and vice president to President Hassan Rouhani.

Iran has notified the International Atomic Energy Agency that it will suspend voluntary "transparency measures," notably inspection visits to non-nuclear facilities, including military locations the U.S. suspects of engaging in nuclear-related programs, if Washington has not lifted the sanctions that former U.S. president Donald Trump reimplemented in 2018.

Top U.S. and European officials have urged Tehran to allow continued UN nuclear inspections and stop nuclear activities that have no credible public use, according to the Associated Press.

In response to Trump's so-called "maximum pressure" action against Tehran, the country started to gradually violate its nuclear commitments under the agreement.

Iran's suspension of voluntary transparency efforts, stipulated in a legislation passed by the conservative-run parliament in December, are set to go into effect on Tuesday, Salehi confirmed on Saturday. But Iran has pointed out that it will not stop cooperating with the IAEA or bar its inspectors.

The 2015 international nuclear agreement is aimed at preventing Iran from making nuclear weapons. The country has vehemently denied it is seeking to develop such an arsenal.