TOPSHOT - A woman walks past a billboard displaying Iran’s national flag at Enghelab Square in Tehran. AFP
Iran's ISNA news agency reported an adviser to Qatar's foreign minister had been dispatched to the Islamic republic.
Another Iranian news agency, Tasnim, said the purpose of the visit was to "go over the latest developments regarding the diplomatic process".
A diplomat with knowledge of the situation told AFP on Sunday that "Qatari negotiators flew to Tehran this morning".
Speaking on condition of anonymity to discuss the sensitive talks, the diplomat said the delegation travelled "to help facilitate the finalisation of the agreement".
Pakistan, which has led mediation to end the months-long war, and the US have indicated an agreement to end the fighting would be signed on Sunday.
But Tehran has cast doubt on that timing, and Iranian media has reported a final decision on the framework is yet to be made.
Iran's Fars news agency said that Tehran has not made a final decision on signing the agreement under discussion with the United States.
"The Islamic Republic of Iran has not yet taken or announced its final decision concerning the memorandum of understanding proposed during negotiations," reported Fars, which is close to Iranian conservative circles, citing "a well-informed source close to the Iranian negotiating team".
The prospective agreement has faced opposition from hardline Iranian figures, who argue that it does not serve Iran's interests and would deprive Tehran of leverage over the strategic Strait of Hormuz.
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