A potential breakthrough in the apparently deadlocked efforts to bring the US back into the nuclear deal with Iran is on the horizon after secret diplomatic talks in Frankfurt this week.

The joint commission, the body that brings together the existing signatories to the deal, will meet virtually on Friday to discuss the outcome of Monday’s meeting amid growing optimism that unexpected progress has been made.

In a statement on Thursday, the EU said the joint commission will be chaired, on behalf of the EU high representative Josep Borrell, by the EU foreign service political director Enrique Mora. “Participants will discuss the possible return of the US to Joint Comprehensive Plan of Action (JCPOA) and how to ensure the full and effective implementation of the agreement by all sides,” the statement said.

Donald Trump unilaterally withdrew the US in 2018 from the deal, under which Iran agreed to limit its enrichment of uranium in exchange for the lifting of economic sanctions.

On Thursday, the state department spokesperson Ned Price said the US welcomed the statement.

“We are ready to pursue a return to compliance with our JCPOA commitments consistent with Iran also doing the same,” Price said.

The US is speaking to partners “about the best way to achieve this, including through a series of initial mutual steps”, he added.

The joint commission – including China, Russia and European states, as well as the EU – meets regularly, but the timing of the announcement suggests positive developments, observers said. The last meeting was on 12 December.

Iran has been demanding the US lift all sanctions and unilaterally return to the deal that it left in 2018.

Although the US had said indirect talks were under way with Iran via European intermediaries, there was little sign of progress.

There was growing frustration in parts of the Democratic party that Joe Biden might have put Iran on the back-burner fearing he could lose Congress support for his ambitious domestic agenda if he moved to lift the economic sanctions imposed by Donald Trump.

The private discussions have focused on agreeing a framework whereby the US could start to lift sanctions in return for specific and verifiable steps by Iran to come back into full compliance with the deal. Iran has taken a series of reversible steps to reduce its compliance including increasing uranium enrichment and reducing the UN inspectors’ access to its nuclear sites.

The US had also sought for the deal at some point to be extended in length and broadened to include other issues, such as regional security, something Iran had rejected.

Some observers fear Biden does not understand the urgency of making progress ahead of Iran’s June presidential elections, where hardliners opposed to the principle of the deal are likely to triumph in a low-turnout election.

Sergei Lavrov, the Russian foreign minister, said he was optimistic the US was willing to compromise. He added: “I very much hope that the anti-Iranian inertia that was observed at first will give way to common sense.”