Western partners in the nuclear talks with Iran in Vienna have to "take certain decisions" in order to reach an agreement, Iran's chief negotiator said on Thursday on Twitter.
"Being near the finish line is no guarantee to crossing it" and sealing an accord, Ali Bagheri Kani said.
"It requires extra caution, much perseverance, additional creativity and balanced approach to take the last step," he added.
Reuters reported last week that a US-Iranian deal was taking shape to revive the pact, abandoned in 2018 by then-US President Donald Trump, who also reimposed extensive sanctions on Iran.
Diplomats said a vague mention of other issues in a draft text of the agreement was a reference to the unfreezing billions of dollars in Iranian funds in South Korean banks, and the release of Western prisoners held in Iran.
Iran on Wednesday urged Western powers to be "realistic" in the talks and said Bagheri Kani was returning to Tehran for consultations, suggesting a breakthrough in its discussions is not imminent.
