During his visit, Gates will get an update from the commanders on U.S. military operations in Iraq, said the spokesman, Army Colonel Gary Keck.

U.S. forces are four months into a troop buildup aimed at quelling sectarian and insurgent violence. The final contingent of troops sent as part of the buildup arrived today.

Agence France-Presse reported that Gates will also urge Iraqi Prime Minister Nuri al-Maliki to move forward on steps to promote political reconciliation. Speaking with reporters on his way to Baghdad, Gates said he was "disappointed with the progress so far" toward reconciliation between Iraq's Sunni and Shiite Muslims, AFP reported.

Gates also expressed the hope that the bombing two days ago of a Shiite holy site in Samarra "won't further disrupt or delay the process," AFP said.

The U.S. has sent about 30,000 additional troops to Iraq as part of a joint American-Iraqi crackdown on violence in Baghdad and Anbar province in the western part of the country.

A Defense Department assessment issued June 13 reported that the overall level of violence in the country hadn't fallen since the buildup, as declining levels in Baghdad and Anbar were offset by increases in other parts of Iraq.