In a televised press conference, al-Ja'fari said he is still supported by the Shi'ite-led United Iraqi Alliance, the dominant bloc in parliament, despite some calls for his removal from within the alliance.
Shi'ite leaders have been struggling to reach agreement on whether to keep al-Ja'fari as their nominee, amid objections from Kurdish and Sunni parties, who blame al-Ja'fari for failing to end sectarian violence.
Efforts to form a government of national unity have been stalled by the dispute.
Iraq's parliament is due to convene on April 20. The assembly had been set to meet April 17 but agreed to a delay to give more time to resolve the issue.