For Maliki, a Shia, it is only his third trip as prime minister to the Sunni-dominated Anbar province.
Bush and Gates are also meeting with Sunni tribal leaders in Anbar for the first time. The tribal sheikhs began cooperating with the U.S. military earlier this year in the fight against al Qaeda in Iraq, causing a dramatic reduction in violence.
By meeting directly with Sunni tribal leaders, Bush gets a chance to tout success in the Anbar province, but he is also sending a message to Maliki. The United States plans to accelerate the effort to work directly with local leaders here and elsewhere in Iraq, even if that means bypassing the central government in Iraq. It's what a senior administration official called the "bottom-up approach."
The surprise visit was conducted under such secrecy that reporters traveling with Gates were only given 24 hours notice to pack their bags and asked to tell only two people about the trip: one editor and one family member.
Reporters were not allowed to discuss the trip with anyone else until more than an hour after Gates had arrived. Defense officials said the reason for the secrecy was security.
Bush will spend a few hours on the ground in Iraq, but will never leave the heavily protected U.S. air base.
White House officials won't say how he got out of the White House, but they say it worked so well the president might just want to try it again.
ABC News' Jonathan Karl and Martha Raddatz contributed to this report.