Hours after bombs killed 24 people, underlining the scale of his task, Maliki said restoring stability was the top priority of a broad coalition whose formation gave Iraq its first fully sovereign government since US troops overthrew Saddam Hussein.
Two days short of a deadline set with Maliki's nomination a month ago, a deal struck late on Friday was backed by most sectarian and ethnic groups. It gave another week for agreement on ministers for the key interior and defence portfolios, as well as a less powerful national security minister.
"We will work (to) ... preserve the unity of the Iraqi people," said Maliki.
US President George W. Bush vowed that the United States would stand by Iraq's new government of national unity.
"Iraqis now have a fully constitutional government, marking the end of a democratic transitional process in Iraq that has been both difficult and inspiring," Bush said in a written statement.
British Prime Minister Tony Blair, who like Bush has invested massive personal political capital in the now widely unpopular war to topple Saddam, said: "I'm obviously deeply relieved we've got a government. "It's been six months of agonising wait to get one."
Running briskly through a 33-point government programme that highlighted security and the economy, Maliki said he would beef up Iraq's army and police so that foreign troops could "go back to their countries" on an "objective timetable".
The United States, which has 130,000 troops suffering almost daily casualties in Iraq, is training Iraqi forces to take over security and allow it to send troops home. Washington has refused to publish a timetable for withdrawal.
The cabinet was approved by a show of hands, minister by minister, after a turbulent start to the parliamentary session, when more than a dozen minority Sunni leaders walked out.
The main Sunni Arab leadership, which controls the bulk of the Sunnis' 50-odd seats in the 275-member chamber, held firm after the walkout by the dissidents. Washington says a Sunni presence at last in a full, sovereign government can draw Saddam Hussein's once-dominant minority away from revolt into politics.
Sectarian wrangling has delayed formation of a government since an election in December. Infighting within Sunni, Shia and Kurdish groups, added to Maliki's difficulties. Days more arguing are likely over the interior and defence jobs, filled respectively for now by Maliki and a Sunni deputy premier.
"Tremendous challenges still lie ahead," said US ambassador Zalmay Khalilzad, a prime mover behind the scenes.
"The future of Iraq will set the course of the future of the greater Middle East. The future of this region will determine the future of the world over the next century."
"No matter who rules, he must lead us to safety. The country is devastated. We hope the government can save what's left," said Jabbar Isho Gorgis, a 42-year-old photographer in Baghdad.
Just hours before parliament sat in the heavily fortified Green Zone, protected by the US military firepower, a bomb killed at least 19 people in Sadr City slum.
In the town Qaim, near the Syrian border, a suicide bomber killed five policemen inside a police station. A further 58 people were wounded in the Baghdad blast, which was typical of al Qaeda.
The bomb targeted men gathered after dawn hoping to be hired for casual labour: "When will this end?" one teenager sobbed as he stood amid pools of blood. "Where is the government?"