VIENNA - Six world powers at a United Nations nuclear meeting on Wednesday sought to step up diplomatic pressure on Iran to allay concerns that it is seeking atomic bombs capability and help avert a new Middle East war.

A day after Israel's prime minister ramped up threats to attack the Islamic state, the United States, France, Russia, Germany, China and Britain proposed that Iran be rebuked over its expanded uranium enrichment program, diplomats said.

The six states - involved in a stalled diplomatic push to convince Iran to curb its nuclear program - submitted a proposed resolution to the 35-nation governing board of the International Atomic Energy Agency (IAEA), which is expected to vote on it later this week.

While the move showed big power unity on the matter, it seemed unlikely to have any immediate impact on policymakers in Tehran, which has pressed ahead with its nuclear work despite increasingly harsh economic sanctions.

Backing by the six powers means approval by the board is guaranteed, but Western diplomats are keen to ensure as broad support as possible in a bid to intensify international pressure on Tehran, which they suspect wants to develop a nuclear weapons capability. Iran says its work is peaceful.

The draft text expressed "serious concern" about Iran's defiance of UN demands to suspend atomic activity which can have both civilian and military purposes.

It voiced particular concern about Fordow, an Iranian enrichment site deep underground where an IAEA report in late August said the Islamic state had doubled its capacity over the last three months, the diplomats said.

Iran says its wants to produce electricity and not bombs. Refined uranium can be used to fuel nuclear power plants. If enriched to a high degree, it can provide the explosive core for a nuclear warhead.

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Israel, believed to be the only nuclear-armed state in the Middle East, sees the chance of Iran developing an atomic bomb as a threat to its existence and has stepped up hints of military action.

Escalating tension with the United States on how to deal with Iran, Israeli Prime Minister Benjamin Netanyahu said on Tuesday that if world powers refused to set a red line for Tehran's nuclear program, they could not demand that Israel hold its fire.

Washington says there is still time for diplomacy and sanctions to make Tehran change course.

In their proposed resolution, the six powers voiced continued "support for a peaceful resolution of the international community's concerns, which could best be achieved through a constructive" diplomatic process.

They said Iran should immediately agree a framework accord with the UN nuclear watchdog to clarify concerns over possible military dimensions to its nuclear program, including granting inspectors access to the sites it needs for their inquiry.

An IAEA investigation into suspected atom bomb research in Iran has made little progress since 2008, with Western diplomats accusing Tehran of stonewalling.

"Iranian cooperation with IAEA requests aimed at the resolution of all outstanding issues is essential and urgent in order to restore international confidence in the exclusively peaceful nature of Iran's nuclear program," the powers said.

Russia and China - which have criticized unilateral Western sanctions on Iran's oil exports - were initially reluctant to agree an IAEA board resolution, diplomats said.

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