Iraq's parliament has endorsed last-minute changes to the draft constitution aimed at winning the support of minority Sunni Arabs in Saturday's referendum.
Officials met on Wednesday to discuss the changes which were part of a breakthrough compromise between Kurdish, Shi'ite and Sunni leaders.
The measure enables parliament next year to consider amendments to the charter, if it is approved in Saturday's vote.
One of Iraq's top Sunni parties, the Iraqi Islamic Party has promised now to back the draft, though other Sunni parties may continue to oppose it.
Iraq's top Shi'ite cleric Grand Ayatollah Ali al-Sistani also urged voters to approve the draft.
Earlier, a White House spokesman welcomed the compromise, calling it a "positive step."
Still, violence ahead of the referendum continued in northern Iraq, where a suicide bomber killed 30 people in a crowd of Iraqi army recruits.