Iran, Russia and the United States reacted positively Tuesday to the opening exchanges in a first day of talks in Vienna aimed at rescuing an international agreement on Tehran's nuclear programme.

US President Joe Biden has said he is ready to reverse the decision of his predecessor Donald Trump to withdraw from the landmark 2015 agreement, negotiated to ensure that Iran never developed a military nuclear programme.

Iran confirmed in January it was enriching uranium to beyond the threshold set by the 2015 nuclear deal at its Fordow plant
Iran confirmed in January it was enriching uranium to beyond the threshold set by the 2015 nuclear deal at its Fordow plant Atomic Energy Organization of Iran / -

And after Moscow gave a positive assessment of the opening of the talks earlier Tuesday Washington's reaction a little later was also upbeat. Iran too, described the opening talks as constructive.

"I can say that overall, the meeting was constructive," the head of the Iranian delegation, Abbas Araghchi, said in a video on Iranian broadcaster Irinn.

The United States was not present at those discussions because Iran has refused to meet the US delegation so long as its sanctions against Tehran remain in place. The European Union is acting as an intermediary.

International powers holds nuclear talks with Iran inside a hotel guarded by police after Washington suggested it could be open to lifting sanctions and returning to the nuclear deal, comments welcomed by Tehran.
International powers holds nuclear talks with Iran inside a hotel guarded by police after Washington suggested it could be open to lifting sanctions and returning to the nuclear deal, comments welcomed by Tehran. AFP / JOE KLAMAR

Mikhail Ulyanov, Russia's Vienna-based envoy to international organisations, said Tuesday's meeting between those parties still in the deal -- Iran, China, Britain, France, Germany and Russia -- had been "successful".

It would take time to restore the agreement, he said.

"The most important thing after today's meeting of the Joint Commission is that practical work towards achieving this goal has started," he tweeted.

Diplomats of the EU, China, Russia and Iran start new talks aimed at salvaging the 2015 nuclear deal. The US is expected to participate indirectly after the Trump administration pulled out of the deal
Diplomats of the EU, China, Russia and Iran start new talks aimed at salvaging the 2015 nuclear deal. The US is expected to participate indirectly after the Trump administration pulled out of the deal APA / LARS TERNES

"We do see this as a constructive and certainly welcome step," US State Department spokesman Ned Price said of the talks a little later.

"It is a potentially useful step as we seek to determine what it is that the Iranians are prepared to do to return to compliance with the stringent limitations under the 2015 deal, and as a result what we might need to do to return to compliance ourselves," he added.

Policemen walk behind an Iranian opposition protester who took part in a rally against the Tehran government near the international Iran nuclear talks in Vienna
Policemen walk behind an Iranian opposition protester who took part in a rally against the Tehran government near the international Iran nuclear talks in Vienna AFP / JOE KLAMAR

Since Trump pulled the US out of the deal with Iran in 2018, re-imposing sanctions on Tehran, the remaining parties have been struggling to save the agreement, as Iran has gradually stepped up its nuclear activities.

Tehran is demanding an end to the crippling sanctions Trump imposed -- before which Iran will not meet the US delegates.

The Grand Hotel in Vienna where bilateral meetings are taking place aimed at salvaging Iran's 2015 nuclear deal. The United States is indirectly participating in discussions in Vienna in an attempt to save the international agreement
The Grand Hotel in Vienna where bilateral meetings are taking place aimed at salvaging Iran's 2015 nuclear deal. The United States is indirectly participating in discussions in Vienna in an attempt to save the international agreement AFPTV / Celine JANKOWIAK

Talks between the delegates from the remaining members of the 2015 agreement will continue Wednesday at the luxury hotel in Vienna, a diplomat familiar with the discussions said.

The US delegation is due to meet in a different high-end hotel, also in downtown Vienna, with EU negotiators acting as go-betweens.

At the same time, two expert-level groups -- on sanctions lifting and nuclear issues -- are working "to identify concrete measures to be taken by Washington and Tehran" to restore the deal, Ulyanov said.

"We need to make the best of this diplomatic space to bring the JCPOA back on track," said a tweet from EU diplomat Enrique Mora, the chair of Tuesday's meeting, referring to the pact by its acronym.

"Our clear goal is to return to full and effective implementation of the agreement by all sides," he added.

Ahead of the talks, US special envoy Rob Malley suggested that the United States could be open to lifting sanctions and returning to the deal, comments welcomed by Iran government spokesman Ali Rabiei.

"We find this position realistic and promising. It could be the start of correcting the bad process that had taken diplomacy to a dead end," he told reporters in Tehran.

Iran confirmed in January it was enriching uranium to 20 percent purity, well beyond the threshold set by the deal.

Rabiei reiterated Iran was ready to reverse the steps it had taken as soon as all sanctions imposed during the Trump administration are lifted.

EU spokeswoman Nabila Massrali warned of a "complex process" ahead, stressing that it was too soon to anticipate the outcome.

Kelsey Davenport, director for Non-proliferation Policy at the Arms Control Association think-tank, argued on the eve of the talks for a "bold first step by both sides" to inject "much-needed momentum" into the process.

Washington, for example, could unfreeze Iranian funds held in foreign banks and facilitate humanitarian trade, and Tehran could stop enriching uranium beyond the levels agreed in the 2015 accord, said Davenport.