Iranian Foreign Minister Mohammad Javad Zarif has said a lasting nuclear deal with Iran has "never been closer."
In a message posted on YouTube late on July 3 (below), Zarif also said that there is “no guarantee" of success.
He was speaking in English from the balcony of the Viennese hotel that is hosting the nuclear negotiations between Iran and world powers.
U.S. Secretary of State John Kerry earlier praised a "genuine effort" by all negotiating sides to seal the accord.
Kerry said the talks "are making progress," but he also spoke of "some tough issues."
Russia's Deputy Foreign Minister Sergei Ryabkov said in Vienna on July 2, "All parties are of the opinion that this matter will be resolved in the coming days."
Chinese Foreign Minister Wang Yi also said on July 3 that there was a "high possibility" that Iran and major world powers would agree to a comprehensive deal.
Negotiators from Iran, Britain, China, France, Germany, Russia, and the United States are working to strike a deal under which Tehran would curb its nuclear program in exchange for sanctions relief.
The parties have given themselves until July 7 to reach agreement.
The six powers want limits on Iran's nuclear programs that could have a military use. Tehran denies it is pursuing atomic weapons.
Earlier, the head of the UN nuclear watchdog said after a visit to Iran that both sides have a "better understanding" in some areas but no breakthrough was reached between the agency and Iran on unresolved issues around Tehran's nuclear program.
"Both sides have a better understanding on some ways forward, though more work will be needed," International Atomic Energy Agency (IAEA) chief Yukiya Amano said in a statement on July 3.
Amano's visit on July 2 -- at Iran's invitation -- aimed at advancing "work towards the resolution of all outstanding issues...including clarification of possible military dimensions," the statement said.
The IAEA will play a crucial role in monitoring and verifying any final deal with Iran.
Amano's trip included meetings with Iranian President Hassan Rohani and the secretary of Iran's Supreme National Security Council, Ali Shamkhani.