BAGHDAD, Aug. 19 (Xinhua) -- Iraq's prominent Shiite cleric Moqtada al-Sadr, outgoing Prime Minister Haider al-Abadi and two other parliamentary blocs formed a core of the largest alliance on Sunday ahead of the new parliament session.

The parliamentary blocs of Sadr-backed Sairoon, Abadi's Nasr, Hikma led by Shiite cleric Ammar al-Hakim and Wataniyah, led by Shiite secular Ayad Allawi, in addition to smaller Sunni parliamentary blocs, held a meeting in Baghdad to discuss forming the largest alliance that would form a government for the next four years, a joint statement by the blocs said.

"We agreed today to form a core for an alliance seeking to form a parliamentary alliance that can form the government. We have decided at this meeting to open up to our other partners to contribute together in the formation of this (largest) alliance," the statement said.

Earlier in the day, Abadi called in a televised speech on President Fuad Masoum to invite the new parliament to hold its first session as soon as possible, and called on the political blocs to accelerate their negotiations to agree on the program of the next government.

Abadi's speech came hours after the Federal Supreme Court ratified the final results of May 12 parliamentary elections, marking the first step toward forming the new Iraqi government.

The approval confirmed the preliminary results of May 12 elections, which showed the Sairoon Coalition backed by Shiite cleric Moqtada al-Sadr was the front-runner and won 54 seats in the upcoming 329-seat parliament.

The ratification will widely open the door for Iraqi politicians to form the next government and would give a push for the tough negotiations by the political blocs to form the largest alliance before the first session of the new parliament.

According to the Iraqi Constitution, the ratification of the results entails outgoing President Masoum to call on the new parliament to hold its first session under the chairmanship of the eldest parliament member within 15 days from the court's ratification.

It will also elect a president of parliament and the president of the republic, who will ask the largest alliance to form a government within 30 days.

On May 12, millions of Iraqis went to 8,959 polling centers across the country to vote for their parliamentary representatives in the first general election since Iraq's historic victory over the Islamic State militant group last December.