Iran urged global powers late Tuesday to drop a UN ban on arms sales to the country, describing it as an obstacle to a deal that was now in its final stages.

The arms embargo was not overly important as Iran had developed its own industry, but global powers "must change their approach on sanctions if they want a deal," Iran's negotiator Abbas Araghchi said on state television, adding the final text and most of the annexes were "almost finished."

"Western nations must be prepared to give up sanctions," Araghchi said.

"The structure of the sanctions must not stay in place. The P5+1 countries must change their approach to the sanctions if they want a deal."

US officials insisted however Tuesday that there would be "ongoing restrictions on arms just like there will be ongoing restrictions regarding missiles" in any nuclear deal, which is to be endorsed by a resolution in the UN Security Council.

Negotiators are already drawing up a draft UN resolution which would also address the nuclear-related bans on arms trade and ballistic missiles, a senior administration official said.

Araghchi said there were only two or three main points blocking a deal, adding "the main text of the accord is almost finished, and there are only a few remaining brackets where ministers need to take a political decision."

Four of the annexes including on sanctions, nuclear cooperation and the Iranian nuclear programme were just about complete, he said.

Ministers were still working on a fifth annexe drawing up a timetable for which actions need to be taken when by both sides.

Araghchi also repeated that the Iran team was not working to any deadline and were ready to stay in Vienna several more days.

"Extending for several months is no longer being considered," he added.