Iran's Foreign Ministry said on Monday it would need to see if there are changes in the U.S. position on sanctions as the two countries negotiate a deal to resolve a decades-long dispute over Iran's nuclear ambitions.

"I regret to inform you that the American side has not yet been willing to clarify this issue," Foreign Ministry spokesperson Esmaeil Baghaei said in a weekly press conference in Tehran.

"It must be clear to us how the oppressive sanctions against the Iranian people will be lifted, to ensure that past experiences are not repeated," he added.

Oman's Foreign Minister Sayyid Badr Albusaidi, who has been mediating between Iran and the Trump administration, presented elements of a U.S. proposal for a nuclear deal between Tehran and Washington during a short visit to Tehran on Saturday.

Iranian and U.S. delegations wrapped up a fifth round of talks in Rome last month. While signs of some limited progress emerged, many points of disagreement remain difficult to bridge, notably the issue of Iran's uranium enrichment.