Isis-led Sunni rebels are in control of a disused chemical weapons factory, Iraqi officials have confirmed.
In a letter to the UN, Iraq said it would be unable to keep to obligations to destroy its chemical weapons.
The Muthanna complex northwest of Baghdad houses remnants of rockets filled with sarin and other deadly nerve agents.
The UN and US say the munitions are degraded and the rebels will be unable to make usable chemical arms from them.
Commitment on hold
In the letter to UN Secretary General Ban Ki-moon, Iraq's UN Ambassador Mohamed Ali Alhakim said the rebels took over the complex on 11 June, after disarming soldiers who guarded the site.
The document stated that Muthanna's surveillance system showed that there was "looting of some equipment and appliances" at the factory, about 70km (45 miles) north-west of the Iraqi capital.
- Began operations in the early 1980s soon after Saddam Hussein took power
- Before the first Gulf War, produced 4,000 tonnes a year of chemical warfare agent
- Mustard gas, sarin and VX nerve agent were among those produced
- Site used by UN inspectors to destroy chemical production facilities and equipment
As a result of the takeover, the letter stated that Iraq was unable "to fulfil its obligations to destroy chemical weapons".
However, it added that the government would resume its commitments "as soon as the security situation has improved and control of the facility has been regained".
It is believed that some 2,500 rockets filled with nerve agents - including sarin and mustard gas - are stored at Muthanna.
The US said nearly three weeks ago that the militants had taken the chemical factory,
In recent weeks, Isis (Islamic State in Iraq and the Levant) insurgents have seized huge swathes of north-western Iraq.
The UN has said at least 2,417 Iraqis, including 1,531 civilians, were killed in "acts of violence and terrorism" in June.
More than a million people have fled their homes as a result of the fighting.