TEHERAN/BRUSSELS - Iran said on Monday it may extend an agreement allowing UN inspectors to monitor some key activities if talks with world powers on its nuclear program continue "on the right track".

Talks have been held in Vienna aimed at getting the United States to return to a 2015 deal abandoned by then-US president Donald Trump and lift sanctions, and to bring Iran back to full compliance with nuclear obligations it retreated from in response.

An agreement reached with the International Atomic Energy Agency in February is due to expire later this month, potentially impeding the talks in the Austrian capital.

Iran's Foreign Ministry spokesman Saeed Khatibzadeh said an option after May 21 could be to extend that date "in case the talks are on the right track and Teheran agrees as well".

"Since we are in no rush to conclude these talks, in addition to not allowing them to drag on ...we do not want any date to prevent our negotiating team from precisely carrying out Teheran's instructions," he told reporters.

The "temporary solution" reached in February allowed UN inspectors access to Iran's declared nuclear sites. But Iran suspended so-called voluntary transparency measures, notably inspections of non-nuclear sites, including military ones suspected of nuclear-related activity.

Teheran also denied the IAEA access to recordings from monitoring equipment the UN agency installed at its sites to verify its compliance.

The Atomic Energy Organization of Iran said cameras would keep running at the sites but the withheld footage would be deleted if US sanctions are not lifted by the end of the three-month period.

Iran's chief nuclear negotiator Abbas Araghchi said on Friday he hoped the Vienna talks could reach a conclusion "in the shortest time possible".

Optimism voiced

In Brussels, Josep Borrell, the EU's high representative for foreign affairs and security policy, said on Monday the negotiations in Vienna to revitalize the Iran nuclear deal are progressing and expressed cautious optimism for an agreement to be reached.

Borrell told a news conference after a meeting of foreign ministers of EU member states that he hoped there will be "nonstop" talks in Vienna to try to clinch a breakthrough on bringing the US back to the nuclear deal with Iran.

"This remains an extremely delicate and intense diplomatic process. I dare to say that I am optimistic. There is a window of opportunity that will stay open for a couple of weeks until the end of the month. But a lot of work is needed, time is limited," Borrell said, adding he hoped "that the negotiations will enter in a phase of nonstop" in Vienna.

Agencies - Xinhua