Iranian lawmakers unveiled proposed legislation Wednesday that a top official said would protect the nation's nuclear interests, but which could become an obstacle in negotiations for a deal this month.

The bill, sponsored by the chairman of parliament's national security and foreign policy committee, was signed by 225 of the country's 290 MPs and faces a vote on Sunday.

"At the moment, the negotiating team is facing excessive demands from the United States," said chairman Alaeddin Boroujerdi.

"This bill is being introduced with the aim of supporting the negotiators... and to protect the red lines drawn up by the supreme leader."

It sets out three criteria that must be met by any deal reached with the United States and five other world powers, which faces a June 30 deadline.

First is the "complete and unified lifting on the day of agreement of all sanctions imposed through the UN Security Council, the US Congress and the European Union."

That condition does not specify if it means the day a deal is struck, signed or implemented.

According to the EU and US, sanctions will only be lifted once international inspectors have verified that Iran's nuclear programme is peaceful, as per an outline agreement of April 2.

Secondly, the bill says that although the International Atomic Energy Agency will be authorised to conduct "conventional supervision" of Iran's nuclear sites "access to all documents, scientists and military/security sites... is forbidden under any pretext."

To ensure Iran's nuclear programme does not have military aims, the world powers are demanding an additional protocol allowing more stringent inspections of other facilities in Iran where nuclear activities may have been conducted.

Thirdly, the bill states: "No limit will be accepted on Iran acquiring peaceful nuclear knowledge and technology and the materials required for research and development."

Under the April 2 agreement, the EU and US both said Iran's research activities would have limits.

The bill was announced a day after one of Iran's top negotiators, Abbas Araghchi, hinted that the talks, about to resume at deputy foreign minister level in Vienna, could go beyond the end of June.

"The date... was selected for the end of negotiations but we will not sacrifice a good agreement for the sake of the schedule," he was quoted as saying by Iranian state television.

Despite the calls from Iranian officials for sanctions to be lifted immediately under the accord, President Hassan Rouhani, has conceded that it could take months.

A deal is likely to include the gradual lifting of certain measures in return for action by Tehran in meeting goals to diminish its nuclear capability.

Western diplomats also say a mechanism is being finalised for how to put UN sanctions back in place if Iran violates a deal.