A landmark UN conference on fighting the spread of nuclear weapons opened its final week Monday with eyes on Iran's efforts to avoid fresh UN sanctions against its nuclear program.

Iran is seen as a test case for the 189-nation Non-Proliferation Treaty (NPT), as it claims its nuclear work is peaceful but is under three rounds of UN sanctions to get it to rein in its nuclear program over fears it seeks the bomb.

The NPT conference here was still struggling to formulate a draft final statement, three weeks after opening on May 3.

Committees met Monday on the three pillars of the NPT -- disarmament, monitoring nuclear programs worldwide to make sure they are not used to make weapons, and promoting the peaceful use of nuclear energy.

The conference is to finalize a draft final statement later Monday and begin a last run of plenary sessions on Tuesday. It closes Friday.

In an effort to avoid new sanctions, Iran struck a last-minute deal with Brazil and Turkey last week on a nuclear fuel swap.

In Vienna Monday, Iran formally notified the UN watchdog International Atomic Energy Agency of this deal.

The bargain is for Iran to ship half of its low-enriched uranium (LEU) out of the country in return for higher grade reactor fuel to be supplied by Russia and France.

When the deal was first offered by the IAEA in October, Iran had less of a stockpile of LEU and would have been shipping out two-thirds of the stockpile.

The US had backed the move in order to guarantee that Iran would not have enough uranium on hand to process further for a first bomb.

Iran would still be left at this point with less than it would need to make a bomb. It has promised to ship out 1,200 kilograms (2,640 pounds) of LEU to Turkey in return for the fuel for a research reactor making medical isotopes.

But Western governments say Iran is still not addressing international concerns about its nuclear program.

And a Western diplomat said Monday that the uranium deal has a key technical flaw as it fails to allocate enough time to make the fuel.

�Getting this fuel in one year is impossible. It takes at least one and a half years to have this,� the diplomat told reporters.

He said that might mean Iran could after one year take its low enriched uranium back �and then wait for the fuel to come six months later... There is something tricky there.�

Washington has pressed ahead at the UN Security Council by circulating a new sanctions resolution.

The to-and-fro over Iran has dominated the conference, even if US President Barack Obama's moves towards disarmament, such as a new strategic weapons agreement with Russia, have given Washington increased credibility.

Non-proliferation analyst Rebecca Johnson said "the review conference has a real chance of being able to adopt a constructively useful -- if not fabulously forward-looking) -- outcome."

Sticking points include whether to set a deadline for disarmament, something nuclear weapons state resist and which is almost certain not to be in any final document.

Another thorny matter is an Egyptian-led proposal to set up a nuclear weapon-free zone in the Middle East.

US and Egyptian officials have been meeting on this for almost two months and will be seeking a compromise in New York that would allow Israel to take part.

Israel is not against such a zone but says it can only come after a peace agreement for the region.

Egypt is promoting the zone, however, as a way to move towards peace, especially since Israel is allegedly the only nuclear weapons state in the Middle East.

Other major areas of dispute at the NPT conference are whether to make tougher nuclear inspections mandatory for all member states and how to penalize states, such as North Korea, that withdraw from the treaty in order to make the bomb.

The NPT, which went into effect in 1970, is in crisis over these issues.

The previous NPT review in 2005 failed to reach agreement but the atmosphere has been better this time around in the twice-a-decade meetings.