Iran is optimistic talks on reviving a landmark 2015 nuclear deal with major powers will bear fruit, provided the US fully resumes its commitments, Foreign Minister Hossein Amir-Abdollahian said Friday.

The deal, which gave Iran sanctions relief in return for curbs on its nuclear programme, has been on life support since 2018, when then US president Donald Trump unilaterally pulled out and reimposed crippling sanctions.

US President Joe Biden has signalled a willingness to return to the deal, but his Secretary of State Antony Blinken warned last week that time was running out and the ball was in Iran's court.

Amir-Abdollahian said Iran was looking for concrete signs from the US that it was ready to resume all of its commitments but said he was confident a deal could be done if it was.

"It is important that we receive signals from the other side, including from the United States, showing that they are intent on returning fully to their commitments," the minister told a news conference in Beirut.

"We are assessing the behaviour of the United States. If it reflects a full return to their commitments, we can be optimistic about the Vienna talks."

The talks in the Austrian capital between Iran and the remaining parties to the agreement -- Britain, China, France, Germany and Russia -- have been on hold since a June election in Iran led to a change of president.

New President Ebrahim Raisi -- an ultraconservative former judiciary chief -- is thought to be less ready than his predecessor Hassan Rouhani to make concessions to the West for the sake of a deal.

Tehran has gradually rolled back its nuclear commitments in response to the US pull-out, and Washington has been demanding that Iran return to its obligations too.

The United States has had no seat at the Vienna talks but has been participating indirectly.

Amir-Abdollahian said in Moscow on Wednesday that he expected the talks to resume "soon".

"We are coming back to the Vienna talks," the minister said in Beirut Friday.

"We are nearing a final decision within the Iranian government. It is very important to the new government that the interests and rights of the Iranian people be fully guaranteed in the talks. We will not waste our time in negotiations."

Amir-Abdollahian also said that Iran was willing to cooperate with the Lebanese government to help the country emerge from a crushing economic crisis that has seen shortages of fuel and electricity, and said Iran was ready to build two power stations in Lebanon.