By Barbara Plett
BBC News, New York
Western concerns about Iran's nuclear programme have so far dominated the latest UN conference on the treaty aimed at stopping the spread and stockpiling of nuclear weapons.
Israel has not signed up to the NPT, so does not attend review conferences
But another state is sharing centre stage at the month-long negotiations in New York to strengthen the Nuclear Non-Proliferation Treaty (NPT), despite its complete absence from the hall.
"Israel's nuclear arsenal stands like the radioactive elephant in the room," says blogger and journalist Khaled Diab.
Israel is widely believed to have between 100 and 200 nuclear warheads. Yet it has never declared them, signed on to the NPT, or opened its nuclear facilities to inspection.
Calls from NPT podiums for it to do all three are common enough. But with the US homing in on the potential proliferation risk posed by Iran, Arab and Islamic states have raised the volume on the threat they say is posed by Israel's actual nuclear arsenal.
Crucially, the debate has galvanised long-standing demands for a nuclear-weapons-free zone in the Middle East.
A resolution to create such a zone was adopted at an NPT review conference in 1995 to win Arab support for the indefinite extension of the treaty. Washington sponsored the proposal, but has done nothing to implement it.
Iran says it favours a Middle East nuclear weapons-free zone
This has been a bone of contention at every NPT conference since. Now the controversy over Iran has made it impossible to ignore.
Egypt, which is taking the lead on the Middle East zone, makes the link explicit.
"If major countries wish to address Iran's nuclear dossier, they can do that by bringing Israel and Iran to the negotiating table," Egypt's UN ambassador Maged Abdel Aziz recently told the Al-Ahram newspaper.
Iran has defied UN resolutions demanding that it halt uranium enrichment, a programme it says is designed to produce nuclear energy, but which the West believes has military aims. At the same time, however, Tehran supports the "immediate and unconditional" implementation of the 1995 resolution, declares the president, Mahmoud Ahmadinejad.
Israel also backs a nuclear-weapons-free zone in principle, but only after peace agreements with all the countries in the region.
And Israeli leader Benjamin Netanyahu has made it abundantly clear that he does not see peace happening any time soon. Israel would consider joining the NPT "if the Middle East one day advances to a messianic age where the lion lies down with the lambs," he told the US TV network ABC.
The US broadly agrees with Israel that conditions for a nuclear-weapons-free-zone do not yet exist in the Middle East.
Yet US Secretary of State Hillary Clinton told the NPT conference that Washington was prepared to support "practical measures for moving toward" such a goal. So are the other four permanent members of the UN Security Council: Russia, China, Britain and France.
It is the agenda of President Barack Obama that has created this shift, say analysts.
He has made a reinvigorated non-proliferation regime a centrepiece of his foreign policy.
He also needs Arab and Islamic support to put pressure on Iran over its nuclear programme. The price of that support has to be tangible progress toward the 1995 Resolution on the Middle East, says ambassador Abdel Aziz.
"Success in dealing with Iran will depend to a large extent on how successfully we deal with the establishment of a nuclear-weapons-free zone," he told UN journalists.
Changing the rules
Egypt says it wants a conference to be held next year at which all regional states, including Israel and Iran, start negotiations on this zone.
That may be too much for the Americans. However, diplomats say Washington may accept a special co-ordinator who would work at preparing the ground for a future conference by holding informal talks with Israel and its neighbours.
After 15 years, Cairo says it is flexible but will not accept window dressing.
"We are not into convening a conference only to see it fail," says ambassador Abdel Aziz.
No-one has any illusions that a nuclear-weapons-free zone is imminent in the Middle East.
Even Egypt accepts it will be a long process, perhaps one that could run parallel to any Arab-Israeli peace talks.
But President Obama's decision to get tough with proliferation may be slowly changing the nuclear rules in the Middle East, both for Iran and for Israel.