BAGHDAD—Iraq's Parliament approved a new cabinet of ministers on Monday

Sept. 8, 2014 3:52 p.m. ET

BAGHDAD—Iraq's Parliament approved a new cabinet of ministers on Monday, ending a monthslong drama to select a new leadership only days before U.S. President Barack Obama lays out his strategy to confront the Sunni Islamist insurrection consuming the country.

The strength of the insurgency was on full display Monday morning, when militants from the Islamic State killed 20 people, mostly Sunni tribal fighters who opposed the group, when they detonated two car bombs in the town of Dhuluiya, about 50 miles north of Baghdad.

The Iraqi parliament's support for the new cabinet will allow Mr. Obama to tell leaders in Congress and the American public that his plan for expanded U.S. airstrikes in Iraq will be supported by an inclusive new government in Baghdad.

Yet despite the appearance of a broad-based agreement, Monday's vote followed days of last-minute wrangling that laid bare the profound ethnic and sectarian differences that are likely to persist or worsen, challenging Iraqi unity even long after the new cabinet sits.

The country's two most sought-after and sensitive ministerial posts, the ministries of Interior and Defense, were left vacant after 11th-hour disputes failed to fill them. Incoming Prime Minister Haider al-Abadi, who was sworn in on Monday, will fill those posts himself temporarily, he said, as lawmakers continue to debate the positions.

The vote also gave outgoing Prime Minister Nouri al-Maliki, who held the country's leadership for eight years, a post as vice president. The mostly ceremonial position will allow the exiting leader to preserve his immunity from prosecution at the hands of his many opponents.

Many Iraqi politicians and foreign leaders fault Mr. Maliki's sectarian policies for favoring the country's Shiite majority and setting the groundwork for the Sunni insurgency that consumed huge parts of the country in June.

Mr. Obama has made expanded U.S. military operations in Iraq contingent upon the country's divided political class agreeing on a government capable of bridging the country's ethnic and sectarian divisions.