Ad Melkert is concerned about how close the elections are
The UN's special envoy to Iraq has said it will be a "Herculean task" to ensure basic standards are met before Iraq's planned national elections in January.
Ad Melkert told the Security Council credible polls were still possible, but he was concerned about the timescale.
Iraq's parliament only recently agreed who would be allowed to vote in the disputed city of Kirkuk.
The poll is seen as an important step if the US can meet its goal of pulling out combat troops by August next year.
Iraq's constitution states the elections must be held in January, but Mr Melkert said the UN had serious concerns about delays.
He told the Security Council: "It is truly a Herculean task to ensure that basic standards can be met."
The UN's 20-strong electoral team had been providing assistance to Iraq's electoral commission, he added.
Debate over the electoral law had centred around the northern, oil-rich city of Kirkuk, which is disputed between Arabs, Kurds and Turkmen.
On Sunday, another potential setback loomed when Vice-President Tariq al-Hashemi threatened to veto the new election law unless changes were made.
He wants to guarantee seats for Iraqis living abroad, many of whom are members of the country's once-dominant Sunni Muslim community.