TEHRAN - The merit of an outline nuclear deal with world powers depends on tough details being settled in coming months, Iran's newspapers said Saturday, with opinions split on the planned agreement.

Conservative outlets maintained their long-held scepticism about negotiations with the United States and other leading countries, but rather than criticising the process outright many questioned who had benefited from recent talks in the Swiss city of Lausanne.

Iran's supreme leader Ayatollah Ali Khamenei, who will have the final say on any deal, has yet to officially comment on the agreed framework for ending the 12-year crisis over Tehran's nuclear programme.

"Lausanne Horse-Trading: Bargain or Bust?" said the front page headline in Kayhan, a hardline conservative daily. Its downbeat editorial argued that Iran had received less than it had given away.

"The agreement speaks of suspension of sanctions and not the lifting of them," wrote its editor Hossein Shariatmadari, who is directly appointed by Khamenei.

"Things that Iran has accepted are clear and verifiable, but what the other side has agreed is vague and subject to interpretation," he added.

French Foreign Minister Laurent Fabius had on Friday drawn attention to the sanctions issue not being settled and noted that Iran would "still have to go all the way" on a deal.

On a similar note, the German Foreign Minister Frank-Walter Steinmeier cautioned: "It's too early to celebrate."

The English language daily Iran News asked on its Saturday front page: "Who is the real winner?"

Reformist media however praised the work of Foreign Minister Mohammad Javad Zarif and his negotiators.

Shahvand, a centrist daily, said Zarif and his team has successfully navigated "a dangerous stretch of the path" in Lausanne toward a deal.

President Hassan Rouhani on Friday said Iran would honour its commitments under any final agreement and promised that it would open a "new page" in the Islamic republic's international relations.

But, stressing that the West must keep its promises, he added: "If one day they want to choose a different path, that choice would also be open to us."

In a sign of the criticism that Rouhani's government may still face, Haghighatpour Mansour, vice president of parliament's national security and foreign policy committee, said Iran's negotiators had overstepped their boundaries.

"We offered Western inspectors a key to our military installations," he was quoted by the Tasnim news agency as saying.

Such a step and ratification of the additional protocol of the Nuclear Non-Proliferation Treaty, a condition of any agreement "are issues for... the parliament," he said.