Talks between Iran and world powers aimed at finalising a deal over Tehran's nuclear programme could go beyond a June 30 deadline, a senior Iranian negotiator said on Wednesday.
US Secretary of State John Kerry and his Iranian counterpart Foreign Minister Mohammad Javad Zarif will meet in Switzerland this weekend as part of a push to seal the deal, US officials said.
With the issue of access to military sites emerging as a potential deal-breaker, Iran's supreme leader Ayatollah Ali Khamenei praised the work of his nuclear negotiators after they came under heavy criticism from conservatives in parliament.
Iran and world powers signed a framework accord on April 2 and aim to agree a final deal by the end of June to prevent Iran from developing an atomic bomb, in exchange for an easing of crippling economic sanctions.
But Iranian negotiator Abbas Araghchi, quoted by state news agency IRNA, said the two sides were "not bound by the schedule".
He added: "We are not at the point where we can say that negotiations will be completed quickly -- they will continue until the deadline and could continue beyond that."
Araghchi has been attending a fresh round of talks between Iranian representatives and officials from the P5+1 group -- Britain, China, France, Russia, the United States plus Germany -- which began in Vienna on Tuesday.
- 'Still disagreements' on text -
"We are trying to have a good agreement with all the details meeting our expectations," Araghchi said, describing the efforts to draw up a final text as "hard work".
On Monday, deputy oil minister Amirhossein Zamani-Nia was quoted as saying that 20 pages of the text had been written "but there are still disagreements and 30 percent of the work remains to be done".
In Washington, US State Department press office director Jeff Rathke told reporters on Wednesday that Kerry and Zarif would meet in Geneva at the weekend as part of "the ongoing EU-coordinated P5+1 negotiations".
Khamenei, trying to iron out public differences on the home front, praised the work of Iran's nuclear negotiators.
The negotiators "are working, making efforts, breaking sweat... to obtain what is in the interests of the country and the regime", he said in a meeting with members of parliament.
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The intervention from Khamenei, who has the final say on all matters of state, came after several deputies accused the negotiators of betraying the Islamic republic by making key concessions.
In footage filmed on a mobile phone and widely circulated on social media, ultra-conservative MP Mehdi Kouchakzadeh went so far as to accuse Zarif of "treason" as leader of the negotiating team.
But Khamenei, quoted on his website, said: "On nuclear issues, our positions are clear and the same as I have expressed publicly... These are the positions of the regime."
Critics accuse negotiators of having accepted demands for international inspections of Iran's military sites, a position which Khamenei has totally ruled out.
- Inspections a must: France -
French Foreign Minister Laurent Fabius warned on Wednesday that France would oppose a final nuclear accord unless it allowed inspections of military sites.
An agreement "will not be accepted by France if it is not clear that verifications can be made at all Iranian facilities, including military sites," Fabius told parliament.
On Tuesday, Yukiya Amano, the head of the UN's atomic watchdog, said Iran had agreed to implementing the Additional Protocol of the Nuclear Non-Proliferation Treaty (NPT) that allows for snap inspections.
"When we find inconsistency or when we have doubts, we can request access to the undeclared location for example, and this could include military sites," the Japanese diplomat told AFP.
"Some consideration is needed because of the sensitiveness of the site, but the International Atomic Energy Agency has the right to request access at all locations, including military ones."
Zarif has said the protocol allows "some access" but not inspections of military sites, in order to protect national "military or economic secrets".
Khamenei called for "mutual respect" -- without accusations and suspicions -- between Iran's parliament and its government.
Members of parliament must maintain a "respectful attitude towards ministers" and the government must avoid insulting deputies, he said.