Iraqi lawmakers have failed to resolve differences over an election law, dampening hopes of holding a vote on time in January and throwing into doubt a partial US troop withdrawal later next year.

Iraq's Sunni Arab vice president, Tareq al-Hashemi, vetoed the election law on Wednesday and sent it back to parliament, sparking fears of an election delay that could affect US plans to end combat operations in Iraq in August.

Instead of addressing Hashemi's demand that the law give more seats to Iraqi refugees and minorities, lawmakers squabbled over whether the veto was legal.

They scheduled a session on Saturday in which they would vote on whether to reject Hashemi's veto and send the law back for approval by the three-person presidency council without changes, said the speaker of parliament, Ayad al-Samarai.

Hashemi, one of Iraq's two vice presidents and part of a presidential council that has veto power over legislation, had sent the law back to parliament after objecting to the first article because it did not give a voice to Iraqis abroad.

Many Iraqis abroad are, like Hashemi, members of Iraq's once-dominant Sunni Muslim community.

Many of them fled when the country descended into sectarian warfare after Sunni dictator Saddam Hussein was ousted in the 2003 US-led invasion, propelling Iraq's Shi'ite majority to political dominance.

Lawmakers must pass a modified law in the next few days to meet a constitutional deadline to hold the ballot in January.

'We have not had any sign of a political consensus over this issue today so we decided to go to a vote over the veto,' Samarai told a news conference.-Reuters