Government spokesman Ali al-Dabbagh said all but one of the 28 Cabinet ministers present in Sunday's meeting, in addition to Prime Minister Nouri al-Maliki, voted in favor of the pact by a show of hands.
The Cabinet has 37 members and it was not immediately clear why some ministers stayed away. Several of them were believed to be traveling abroad.
Al-Dabbagh said the agreement will be submitted to parliament later Sunday, but did not say when the 275-member legislature will vote on the document.
The Cabinet vote came a day after the country's most influential Shiite cleric, Grand Ayatollah Ali al-Sistani, indicated that he would not object to the pact if it is passed by a comfortable majority in parliament. That cleared a major hurdle to the agreement.
The final draft of the agreement, reached after months of negotiatiwons, is designed to meet Iraqi concerns over its sovereignty and its security needs as it continues to grapple with a diminished but persistent insurgency.
It provides for the departure of U.S. forces from Iraq by the end of 2011 and gives Iraq the right to try U.S. soldiers and defense contractors in the case of serious crimes committed off-duty and off-base. It also prohibits the U.S. from using Iraqi territory to attack Iraq's neighbors, like Syria and Iran.
Proponents of the security pact with the Americans, including al-Maliki's interior and defense ministers, say a continued U.S. military presence is needed until Iraq's nascent security forces are capable of taking charge of security in the war-devastated nation.
Sunday's Cabinet session began shortly after a roadside bomb killed three people and wounded seven in a northern Baghdad district, the latest evidence that violence continues to plague Iraq despite the dramatic improvement in security over the past year.
The roadside bomb hit a checkpoint belonging to U.S.-backed fighters in the Sunni enclave of Basatin in the predominantly Shiite Shaab district, according to police and hospital officials who spoke on condition of anonymity because they are not authorized to speak to the media.
Two of those killed were members of the local Awakening Council, or Sahwa, one of several names used to refer to the Sunni insurgents and tribesmen who have revolted against al Qaeda in Iraq, joining the U.S. military in the fight against the terror group.
Five of the injured were also Sahwa members.
Sahwa fighters have been frequently targeted by al Qaeda militants since they changed sides in late 2006, with scores of their leaders assassinated and their checkpoints and headquarters bombed.
By Associated Press Writer Qassim Abdul-Zahra