The U.S. military had freed 1,000 detainees from Iraq's Abu Ghraib prison

The U.S. military said on Saturday it had freed 1,000 detainees from Iraq's Abu Ghraib prison at the Baghdad government's request, in the largest release to date.

It was not clear if the decision was linked to a demand by Arab Sunnis opposed to a draft constitution that authorities release Sunni prisoners so they can participate in a referendum on the text and elections later this year. Negotiations on the constitution, involving leaders from rival sectarian and ethnic groups and U.S. diplomats, continued amid a battery of conflicting public statements. There were signs of splits within the Sunni camp, with other delegates saying that some Sunnis had been won round to a compromise proposal from the Shi'ite and Kurdish-led government while some Sunni leaders said they saw nothing to agree on.

But one leading Sunni figure, Saleh al-Mutlak, said he had not even seen the document. It remained unclear what would happen next or even if parliament would meet on Sunday to review the draft after Sunnis respond to the proposed changes, as parliament speaker Hajem al-Hassani said late on Friday and repeated on Saturday. Later on Sunday, some delegates cast doubt on whether the timetable would hold after two weeks of missed deadlines.

Sunnis are fiercely opposed to a constitution which enshrines federalism, fearing it would give the Shi'ite and Kurdish leaders who dominate the government control over oil resources in northern and southern Iraq, Reuters reports.