A statement from Jalal Talabani's office on Sunday said: "The presidency council took this decision after consulting all parties involved, in order to give the security forces time to ... prepare for the (Shia ceremony of) Arbain."
Talabani had originally said that he would call for the parliament to convene on 12 March, but the powerful Shia Alliance asked for a delay until 19 March because it needed more time to negotiate on the formation of the new government.
Iraq's political leaders are deadlocked over who should be prime minister in the new government. Sunnis and Kurds are opposed to Ibrahim al-Jaafari, the prime minister and a Shia, staying on in the powerful post. Al-Jaafari insisted on Sunday he would stay.
Iraqi officials said they expected the first session of parliament to discuss little substantial business, with hopes fading of leaders reaching a deal on a government by then.
The Shia Alliance, which has close to a majority in the parliament elected in December, said it was determined to resist the efforts to oust al-Jaafari.
Sunni and Kurdish parties accuse al-Jaafari of failing to improve security or prosperity in the year he has been interim prime minister.
Al-Jaafari, leader of the Dawa party, won the nomination to lead the new government by a single vote in an internal ballot of alliance legislators.