UNITED NATIONS, April 20 (Reuters) - Israel may come under new pressure next month at a UN meeting on atomic weapons as the United States, Britain and France consider backing Egypt's call for a zone in the Middle East free of nuclear arms, envoys said.

The 189 signatories to the 1970 Non-Proliferation Treaty (NPT) will meet at UN headquarters in New York for a May 3-28 conference on the troubled pact whose credibility, analysts say, has been harmed by the atomic programs of Iran and North Korea and the failure of the big nuclear powers to disarm.

Israel, like India and Pakistan, never signed the treaty and is not officially attending the conference. The Jewish state is presumed to have a sizable nuclear arsenal, although it has never confirmed or denied having atomic weapons.

NPT review conferences take place every five years. At the 1995 meeting, member states unanimously supported a resolution backing the idea of a Middle East zone free of nuclear weapons as well as other weapons of mass destruction.

In a working paper Egypt submitted to fellow treaty members ahead of next month's meeting, Cairo said the conference should formally express regret that no progress has taken place on the implementation of the (1995) resolution and call for an international treaty conference by 2011.

The point of such a conference would be to launch negotiations, with the participation of all states of the Middle East, on an internationally and effectively verifiable treaty for the establishment of a nuclear-weapon-free zone in the Middle East, the Egyptian paper says.

Egyptian initiatives at NPT meetings are nothing new.

But Western diplomats familiar with the issue said the five permanent UN Security Council members -- the United States, Britain, France, China and Russia -- might be ready to support such a conference, although not with a negotiating mandate.

The diplomats, who spoke to Reuters on condition of anonymity, said the three Western powers might also encourage Israel to participate, although their position was that there could be no mandate for negotiating such a treaty now, when many countries in the region refuse to recognize Israel.

Egypt is one of several Arab states that recognize Israel.

SHIFT IN U.S. APPROACH

Diplomats said backing from the five permanent Security Council members -- the NPT's five official nuclear powers -- would help ensure broad support for Egypt's plan next month.

One Western envoy said Egypt's insistence on a conference with a negotiating mandate was the main sticking point, while another expressed the hope that Egypt would compromise during intensive negotiations on the issue in the coming weeks.

But Egypt's UN Ambassador Maged Abdelaziz told Reuters the sticking point was Israel's reluctance to participate.

We want the Israelis to sit at a table and negotiate, he said.

We're flexible on the location and the format of the conference, Abdelaziz said, adding that one possible idea was to have UN Secretary-General Ban Ki-moon oversee it.

Western diplomats said the US willingness to entertain the idea of supporting such a conference highlighted the sharp shift in Washington's approach to Israel under President Barack Obama compared with his predecessor George W. Bush.

US support for a regional nuclear conference could further alienate the Israelis at a time when relations are already tense due to disagreements over Israel's settlements policy in occupied areas the Palestinians want for a state.

One Western diplomat said the Israelis were understandably reluctant to take part, even if the conference's outcome would be merely symbolic. But it would be difficult to refuse if Washington began to put pressure on the Israelis, he said.

They (the Israelis) have an interest here, another diplomat said. If the Arabs get something they want on Israel, they'll be more supportive on Iran's nuclear program and further sanctions. Israel would benefit from that.

Israel, like the United States, European Union and others, suspects Iran is developing atomic weapons, a charge Tehran denies. Iran, whose president has said Israel should be wiped off the map, says its nuclear program is peaceful.

Israel's UN mission had no official comment on the Egyptian proposal. But an Israeli diplomat told Reuters the Jewish state will be ready to discuss issues like establishing a nuclear-weapon-free zone once there is peace in the Middle East.

Several diplomats told Reuters that Egypt has made clear it sees Israel as a higher priority than Iran and has threatened to prevent the NPT conference from reaching any agreements next month if it does not get what it wants on Israel. Decisions at NPT meetings are made by consensus.

The 2005 NPT review conference, which was widely seen as a failure, was unable to reach any agreements after Washington worked to focus attention on Iran and North Korea, while Egypt and Iran attacked Israel and accused the United States and others of reneging on disarmament promises. (Additional reporting by Sylvia Westall in Vienna; Editing by John O'Callaghan)