The deal, which the Iraqis and Americans hope to finish by midsummer, would establish a long-term security relationship between Iraq and the United States.
Critics however say it will allow Washington to set up military bases across Iraq and allow the U.S. to use the country as a launching pad for military attacks in the region.
Washington and Baghdad are also negotiating a parallel agreement to provide a legal basis for keeping U.S. troops in Iraq after the United Nations mandate expires at the end of the year.
The Independent newspaper in London reported Thursday that Iraqi officials are worried that the White House agreements, which are being pushed without approval by the U.S. Congress, would have "an explosive political effect" in Iraq.
The paper said leaked details about the agreements include U.S. troops occupying permanent bases in the country as well as the ability to conduct military operations, arrest Iraqis and receive immunity from Iraqi law. It reported that Iraqi officials fear the accord would lay the basis for "unending conflict" in their country.
Ahead of the two-day visit, al-Maliki's party sought to calm worries by insisting that the deal would not allow foreign troops to use Iraq as a ground to invade another country - a clear reference to Iranian fears of a U.S. attack.
U.S. Congressional Democrats have urged the Bush administration not to bypass Congress, which they believe should approve any deal.
They fear a long-term security deal with Iraq - if it committed the U.S. to protecting Iraq - could make it difficult for the next president to withdraw U.S. forces from Iraq.
The toughest words have come from Iraqi officials, especially those loyal to Muqtada al-Sadr, the anti-American cleric whose militiamen fought U.S. and Iraqi troops in Baghdad until a May truce ended seven weeks of fighting.
Tens of thousands took to the streets in Baghdad's Shiite slum of Sadr City on Friday to protest against the agreement.
Supporters believe the deal would guarantee U.S. support as Iraq seeks to cement the security gains of the past year.
It would also help assure Iraq's Sunni Arab neighbors, notably Saudi Arabia, that Iraq's Shiite-led government would not become an Iranian satellite.
U.S. officials have released no details about the negotiations, which began last March, but the U.S. alleges that Iran is encouraging a public campaign in Iraq against the proposed security agreement, which the Iranians oppose.
Al-Maliki's Dawa party has described the talks as stalled and prominent parliamentarians from Shiite, Sunni and Kurdish parties have written to Congress to express their opposition to the proposed agreement, which must be approved by the Iraqi legislature.
In Other Developments:
Iraqi police said two car bombs exploded in central and western Baghdad, killing at least four people. They said one was a suicide car bomb targeting a police patrol in Nisoor Square on the capital's west side. Police said a civilian and a policeman were killed and five other people were wounded.
The other blast took place Saturday afternoon at a small bus station in central Baghdad, killing two civilians and wounding nine. The station is a hub for buses heading east into Shiite neighborhoods.
Iraq Oil Minister Says Security Allowed Oil Boost
Iraq's oil minister said improved security has allowed the country to boost its oil production to pre-war levels.
Oil Minister Hussain al-Shahristani said the increase has enabled Iraq to earn nearly $28.5 billion in revenues in the first five months of this year.
Production last month hit the pre-war level of 2.5 million barrels a day. Al-Shahristani told parliament that in the coming five years, Iraq should be able to produce between 4 and 4.5
million barrels a day.
Security in the oil-producing areas of southern Iraq has improved since the government launched a crackdown on Shiite militias in late March.
U.S. Kills 4 Suspected Militants, Captures 5
The U.S. military said it has killed four suspected militants, captured five others and destroyed
two safehouses in northern Iraq.
A statement from the military said American soldiers called in airstrikes and killed the four men Saturday after coming under small-arms fire southwest of Mosul. They also destroyed two
buildings filled with weapons, ammunition and graffiti indicating they were used for foreign militants.
The military said five men were captured in a separate raid in Mosul. Two of them are accused of conspiring with senior al Qaeda in Iraq leaders in the city.
Mosul is believed to be one of the last urban strongholds of the terror group, and U.S. and Iraqi forces have fought fierce battles against militants there in recent months.