The UN nuclear watchdog, the IAEA, says it has frozen almost half its technical aid projects involving Iran.
Iran says it nuclear programme is for peaceful purposes
The IAEA says its move is to comply with UN sanctions imposed on Tehran late last year over its refusal to halt uranium enrichment.
Twenty-two projects have been suspended, according to an IAEA report.
Iran's chief nuclear negotiator, Ali Larijani, is to meet EU diplomats at a forum in Germany on Saturday, despite earlier reports to the contrary.
European officials hope to hold informal talks with him on the nuclear stand-off at the top-level security conference in Munich.
'Message of inducement'
The IAEA gives technical aid to dozens of countries on the peaceful use of nuclear energy in fields such as medicine, agriculture and power generation.
The nuclear watchdog has 55 projects that involve Iran.
Of these, 22 have now been frozen to comply with the UN sanctions, which call for an end to programmes that could be exploited by Iran to develop nuclear weapons.
The IAEA board is expected to formally back the move, recommended by IAEA chief Mohamed ElBaradei, when it meets next month.
The BBC's Kerry Skyring in Vienna says that the IAEA has been under pressure from the United States to take a tough line.
A senior UN official told Reuters news agency the freeze constituted a "substantial cut" in technical aid to Iran.
"It is a message of inducement to Iran to reconsider its course," the official said.
The US believes that Iran is working to develop nuclear weapons. Iran says its nuclear programme is for peaceful purposes and has vowed to continue.