Israeli Prime Minister Benjamin Netanyahu slammed the international community's "rush to accommodate" Iran on Monday, describing an easing of sanctions against the country as dangerous "political theatre."

"There is a rush to accommodate Iran as if it has changed anything in its policies. The Iranian regime, though it smiles, continues to butcher people in Syria and sponsor terrorism," Netanyahu said after talks with Italian Prime Minister Enrico Letta.

While Letta said he was "cautiously hopeful" negotiations to curb Iran's nuclear programme would be successful, Netanyahu restated his firm opposition to an international deal with Israel's arch-foe.

"Great work has been done over the past decade in putting powerful, binding sanctions on Iran," Netanyahu told a press briefing.

"These sanctions have been eased, but for what in return? We need substance, we cannot be satisfied with political theatre," he said.

Iran has agreed to freeze its nuclear programme for six months in exchange for limited sanctions relief following marathon talks in Geneva last month.

US President Barack Obama's administration has argued that the preliminary deal will help ensure the security of the Middle East region as it seeks to nail down a comprehensive settlement with Iran.

Iranian President Hassan Rouhani, who was elected earlier this year, has promised a more diplomatic approach to the West after eight years of stalled talks and escalating sanctions under his hardline predecessor, Mahmoud Ahmadinejad.

But Israel has slammed the deal as an "historic mistake" and US Secretary of State John Kerry is due in Israel this week to try to ease tensions.

Tehran has a long history of belligerent statements toward the Jewish state, and Israel -- the Middle East's sole if undeclared nuclear power -- has warned that a nuclear Iran would pose an existential threat.

"We are in danger, peace in Europe and across the globe is in danger. We need real change, a real roll-back, because if Iran continues towards the bomb it will be a pivot of history," Netanyahu said.

The Israeli PM said he had spoken to Letta -- and earlier to Pope Francis -- about negotiations for peace between Israel and the Palestinians.

"We want peace, we pray for peace, we are working for peace. We hope we have a partner for peace on the other side," he said.

"In addition to the political conditions that have to be met, we want to ensure a sound basis of security," he added.

Talks between Israel and the Palestinians resumed in July after a three-year hiatus but have faltered due to Israeli plans for new settlement building.

The Vatican said the pope's 25-minute audience with Netanyahu earlier Monday had addressed "the complex political and social situation in the Middle East, with particular reference to the resumption of negotiations between Israelis and Palestinians."

The pope expressed a hope "that a just and lasting solution, which respects the rights of both parties, can be reached as soon as possible", it said.

The Israeli PM gave the pope a book dedicated to "Pope Francis, a great shepherd of our common heritage".

Francis is expected to travel to the Middle East next year and Israeli sources say the visit could take place before Israeli President Shimon Peres ends his term in July.

Although no date has been made official, sources on both sides say it is likely to take place on May 25-26.

Israel and the Vatican first established full diplomatic relations in 1993, but have been engaged in years of thorny diplomatic negotiations over property rights and tax exemptions for the Catholic Church, which have yet to be fully resolved.