Iran’s chief negotiator at the Vienna nuclear talks met Thursday with the three European participants in the 2015 nuclear deal, before negotiations take a New Year recess.

The Islamic Republic News Agency (IRNA) reported the meeting saying that the European Union representative at the talks Enrique Mora also took part in the meeting with diplomats from the United Kingdom, France and Germany.

Negotiations began in April to revive the Joint Comprehensive Plan of Action, or JCPOA, to bring the United States back into the agreement after former US president Donald Trump withdrew from the deal saying it was inadequate to prevent Iran from acquiring nuclear weapons.

IRNA reiterated recent optimism expressed by Tehran and Moscow about the chances of an eventual agreement, although the United States and the European troika (E3) have been guarded regarding Iran’s conduct in the negotiations, demanding a faster process.

World powers remaining in the agreement, Russia, China and the E3, met with US representatives in Vienna on Wednesday. The US is not directly participating in the formal JCPOA meetings but is in essence negotiating with Iran through its European allies.