"We think (the talks) can reach their goal," he told reporters in Madrid after a gathering of the Stockholm Initiative, a group of 16 states working towards nuclear disarmament.

"I think we'll get there in the coming weeks," Maas added of the Iran talks that resumed in April in Vienna.

The negotiations aim to save the deal -- known to diplomats as the JCPOA -- between Iran and the five permanent UN Security Council member states plus Germany.

Under the Trump administration, the US walked away from the accords designed to prevent Iran from developing a nuclear weapon.

Following the Stockholm Initiative meeting in Madrid, member countries "renewed their appeal to all states possessing nuclear weapons... to promote disarmament by adopting significant measures" to comply with the global Non-Proliferation Treaty (NPT), they said in a statement.

Stockholm member states' foreign ministers were meeting ahead of the next Review Conference on the NPT, which has been delayed until early next year due to the coronavirus pandemic, Spain's foreign minister Arancha Gonzalez Laya said.

The initiative's members include current co-chairs Germany, Spain and Sweden as well as Argentina, Canada, South Korea, Ethiopia, Finland, Indonesia, Japan, Jordan, Kazakhstan, Norway, New Zealand, the Netherlands and Switzerland.