Iran has denied any talks are ongoing with the US despite a claim from Donald Trump, who called off strikes on the country on Saturday.
Trump had announced that negotiations with Iran would begin on Monday after he decided to hold off on new strikes against the Islamic Republic in order to pursue a deal.
"Obviously, they don't want to be attacked," Trump told reporters on Sunday on board Air Force One.
"Now what we're doing is we're talking to them in the form of a negotiation. It begins tomorrow afternoon."
However, Iran's foreign ministry has said there were currently no negotiations with the US but that talks were taking place with Oman over the Strait of Hormuz.
The Foreign Ministry spokesperson, Esmaeil Baghaei, said discussions with Oman were "constructive" and aimed at reaching an agreement on a new route.
"We are not currently negotiating with the United States. Our negotiations are with Oman to secure passage through the Strait of Hormuz," Baghaei said during a press briefing.
"We hope that both regional and extra-regional actors will appreciate this responsible move by Iran and adopt a constructive approach."
He added that as long as a US naval blockade on Iranian ports continues "the situation in the Strait of Hormuz will remain unchanged".
Despite the conflicting statements, oil prices fell sharply on Monday following Trump's statement.
At around 09.15 GMT the price of a barrel of North Sea Brent crude for October delivery – trading as the benchmark contract for the first time – was down 4.59 percent at $83.89.
On Sunday, Saudi Arabia's state media said Crown Prince Mohammed bin Salman had spoken to Trump over the phone on developments in the region.
The crown prince reportedly stressed "the necessity of prioritising dialogue to de-escalate tensions and the importance of exerting all possible efforts to achieve a truce, which paves the way for diplomatic solutions".
He also said diplomatic solutions should "yield positive results for preserving the security and stability of the region and prevent it from being drawn into a wider conflict".
The conversation came after Saudi Arabia expressed concern over Trump's plans to strike Iran.
The conflict between the US-Israel and Iran, which began in February, has left thousands of people dead and caused massive economic damage particularly in the Gulf states, which have faced repeated attacks from Iran.
The closure of the Strait of Hormuz has been particularly disruptive to the region's economy, and the long-term reopening of the waterway has been a primary goal.
A spokesperson for Iran’s parliamentary National Security Committee, Hassan Qashqavi, said on Monday that Tehran was close to reaching an agreement with Oman over the strait.
He also confirmed that the country's mediators were seeking to revive the Memorandum of Understanding with Washington.
