The painstakingly negotiated 2015 accord saw Iran granted relief from international sanctions in exchange for accepting limits on its nuclear programme aimed at easing fears it could acquire an atomic weapon.
Biden has promised to rejoin the agreement on condition Iran first returns to respecting commitments it abandoned in retaliation for Trump pulling out and re-imposing swingeing sanctions.
Tehran says Washington has to end the sanctions before it will make any moves to get back in line, and is refusing to hold direct negotiations with the US.
Iranian foreign minister Mohammad Javad Zarif insisted the aim of the talks was to "rapidly finalise sanction-lifting and nuclear measures for choreographed removal of all sanctions, followed by Iran ceasing remedial measures".
"No Iran-US meeting. Unnecessary," he wrote on Twitter.
US State Department spokesman Ned Price called the Vienna talks a "healthy step forward" and said Washington "remains open" to a direct encounter with Tehran.
He cautioned that "these remain early days, and we do not anticipate an immediate breakthrough as there will be difficult discussions ahead".
The deputy State Department spokeswoman, Jalina Porter, said sanctions relief steps will be "up for discussion" but declined to elaborate further.
Substantial work ahead
EU diplomat Enrique Mora described Friday's virtual meeting that he chaired as "positive", but warned that there was much left to do to revive the deal.
"Substantial work ahead for a key opportunity to bring JCPOA back to life," he tweeted, using the acronym for the nuclear deal's formal name.
A senior EU official said Brussels -- which acts as coordinator -- hoped to see a final agreement on a US return to the deal within the next two months.
The official said two groups of experts from the remaining participant countries would work simultaneously, with one focused on US sanctions and the other on rolling back Iran's breaches.
German foreign minister Heiko Maas said it was "good that all the relevant actors would meet in Vienna next week".
"We have no time to waste. A treaty that is fully respected once again would be a plus for security throughout the region," he said.
Russian diplomat Mikhail Ulyanov said "the impression is that we are on the right track but the way ahead will not be easy and will require intensive efforts. The stakeholders seem to be ready for that".
"Possible US return to JCPOA apparently will require Washington's full compliance with the nuclear deal," he wrote on Twitter.
In 2018, Trump dramatically withdrew from the pact and re-imposed crippling economic sanctions on Tehran. The following year, Tehran announced it would start breaking limits agreed on nuclear activity.
The remaining participants in the deal have scrambled in recent years to salvage it from total collapse as Tehran has made good on its threat, while insisting it is not seeking a nuclear weapon.
Some analysts have seen Biden's hesitation at immediately removing sanctions as a way to pressure Iran -- or a way to preserve political capital for other priorities as the nuclear deal remains fiercely opposed by Trump's Republican Party.
Republicans quickly pounced on news of the Vienna meeting. Senator Tom Cotton, who has called in the past for attacking Iran, tweeted that the Biden administration was "so desperate to get back to a broken deal that they're giving up all their leverage and offering concession after humiliating concession."
But some observers saw the Vienna meeting as a way to break the logjam and return to an accord with which UN inspectors say Iran was complying before Trump trashed it.
"Proximity talks are a creative solution to overcoming the current impasse," said Suzanne DiMaggio, a senior fellow at the Carnegie Endowment for International Peace.