Ahmad Dastmalchian, the former Iranian ambassador to Lebanon, said that United States seems to have asked Oman for mediation between Iran and them.
He added: "United States tries to find a way to open dialogue with Iran through Switzerland and Oman."
The foreign minister of Oman, which in the past helped pave the way for negotiations between Iran and the US, made a surprise visit to Iran on Monday, amid heightened tensions between the US, Saudi Arabia and the Islamic Republic.
"But Iran has no confidence in the United States, and the negotiation is impossible, so there is no way of mediation,"a former Iranian diplomat said.
He stressed that there is only one possibility of returning to the negotiating table so Washington must accept Iran's deal again, lifting the oil embargo and removing the Islamic Revolutionary Guard from the list of terrorist groups.
Yousuf bin Alawi bin Abdullah discussed regional and international issues with Iranian Foreign Minister Mohammad Javad Zarif. It was not clear if the visit was aimed at calming Iran-US tensions.
As a Persian Gulf Arab state that maintains friendly ties with both the US and Iran, Oman has previously been an important go-between for the two countries after they severed diplomatic relations in 1980.