Iran's supreme leader Ayatollah Ali Khamenei restated his red lines for a nuclear deal with world powers in a sudden intervention Tuesday after discord surfaced between his government and lawmakers.

Khamenei, who will have the last word for Iran in its talks with the West, stepped in hours after Iran's parliament passed a bill on the country's nuclear programme which a vice president said could complicate the final leg of the long-running negotiations.

The move by lawmakers exposed tension between President Hassan Rouhani's administration and lawmakers in Tehran, where hardliners routinely voice doubt about the merit of talking to the West.

With obstacles remaining just one week until the June 30 deadline for a nuclear deal, Khamenei outlined his demands at a top level meeting that included Rouhani and Mahmoud Ahmadinejad, the president's hardline conservative predeccessor.

Banking and economic sanctions imposed on Iran by the United Nations or US Congress must be lifted immediately when an agreement is signed, Khamenei said, according to a transcript of remarks published on his official website.

"Other sanctions can be removed gradually by a reasonable timetable," he added, noting cancellation should not be linked to implementation by Iran of its commitments, a remark that led him to outline what international monitoring would be allowed.

Describing the International Atomic Energy Agency (IAEA) as "neither independent or fair", Khamenei said Iran would not permit inspections at military sites or "unconventional inspections" at other facilities, which he did not name.

He also called into question the duration of limits under a final accord. A preliminary framework agreed on April 2 stated that Iran's enrichment of uranium would be curtailed for 10 years, with other parts of its nuclear activities being curbed for longer.

Noting that some restrictions were acceptable, "extreme demands" were not, Khamenei said.

"Unlike the insistence from the Americans, we do not accept long-term limitations of 10, 12 years. And we told them how many years (of) limitations we are ready to accept," he added.

Under the preliminary framework, the P5+1 powers (Britain, China, France, Russia and the United States plus Germany) Iran's enrichment of uranium would be conducted exclusively at its Natanz facility.

According to the transcript -- Khamenei's comments at the meeting were later circulated in a series of messages on his Twitter account -- Iran must also be allowed to continue its nuclear research and development.

- Talks entering final lap -

Although Khamenei said he backed Iran's negotiators, headed by Foreign Minister Mohammad Javad Zarif, his sudden remarks so close to the deadline are likely to trigger strong reaction from opponents of a nuclear agreement with the Islamic republic.

Those include Israel's Prime Minister Benjamin Netanyahu, who warned the US Congress in March against ratifying "a bad deal".

Rouhani, a moderate who aims to end Iran's diplomatic isolation, wants an accord that can lift sanctions that have hobbled the economy, but the bill passed by parliament earlier Tuesday underlined the resistance he faces.

One of his vice presidents, Majid Ansari, said the draft legislation, which still has to be signed into law by Iran's Guardian Council, was unconstitutional and would not help at "a sensitive point" in the talks.

"The engagement of MPs on this issue is of no help to the nuclear team and it could create problems in the negotiation process," he said.

The bill lays down terms for MPs' accepting a deal, but Ansari said any nuclear agreement was a defence and strategic issue reserved for Iran's Supreme National Security Council, a body of ministers, generals and Khamenei appointees.

It is chaired by Rouhani. Zarif is also a member.

Domestic critics of Rouhani's nuclear policy, including in the conservative-dominated parliament, say too many concessions have already been made in the talks and, using the bill, they demanded a bigger say.

Bargaining over a final deal intensified Monday when Britain and France reiterated that comprehensive inspections of Iran's nuclear facilities are essential to prove its nuclear activities do not have military dimensions.

Western powers have long suspected that Iran is covertly developing an atomic bomb, an allegation it denies.

President Barack Obama has given US lawmakers 30 days to review any deal.