“The atmosphere was constructive. Discussions were good,” Araqchi told reporters on Sunday.
"I cannot say that we resolved everything," he said, adding that but all the parties are still "determined to save this deal."
The parties met in Vienna for talks called in after Iran began to scale back its commitments to the landmark nuclear deal more than a year after the US withdrew from the accord and reinstated sanctions on the Islamic Republic.
Representatives from Germany, France, Britain, China, Russia and the European Union participated in the meeting.
Iran wants the remaining parties to the deal to offset sanctions US President Donald Trump reimposed.
"As we have said, we will continue to reduce our commitments to the deal until Europeans secure Iran's interests under the deal," Araqchi said.
The remaining signatories and Iran have been trying to salvage the pact since the US withdrawal.
The Europeans say a breach of the agreement by Iran would escalate confrontation at a time when Tehran and Washington are at risk of a miscalculation that could lead to war.
However, their efforts to protect trade with Iran against the US sanctions have yielded nothing concrete so far.
Iran has called on Europe to accelerate its efforts.
"All our steps taken so far are reversible if other parties to the deal fulfill their commitments," an Iranian diplomat told Reuters before the meeting was due to start.
Under the deal, most international sanctions against Iran were lifted in return for limitations on its nuclear work.
So far, Iran has crossed the limit of its enriched uranium stockpile as well as enriching uranium beyond a 3.67 percent purity limit set by its deal with major powers.
The UN nuclear watchdog, policing the deal, has confirmed the measures announced by Tehran.
The meeting in Vienna comes after Iran’s Islamic Revolution Guards Corps seized a British-flagged oil tanker on July 19, two weeks after British forces captured an oil tanker filled with Iranian crude near Gibraltar.
Araqchi said Britain’s seizure of the Iranian oil tanker was a violation of the nuclear pact.
“We witnessed the seizure of an oil tanker carrying Iranian oil in the Strait of Gibraltar which in our view is a violation of (the nuclear deal),” Araqchi said.
“And the countries who are part of (the nuclear deal) shouldn’t create obstacles for the export of Iranian oil.”
Reuters and AP contributed to this story.