En route to the war zone, Gates said it "remains to be seen where we'll be in September" when he is to make an assessment of whether the Iraqi government is making the kind of progress demanded by the Bush administration and an increasingly impatient Congress.
His cautious tone reflected a growing sentiment among military leaders that they may not be ready to make a full review of the effects of the U.S. troop buildup that President Bush ordered early this year to try and stabilize Iraq.
"It may still be that there will be a lot of uncertainty, but I think we'll have some sense of direction and trends on where things are headed," Gates said.
His fourth visit to Iraq since becoming Pentagon chief last December comes as criticism of the U.S. military, including the top general in Iraq, is rising in Congress. Senate Majority Leader Harry Reid said Thursday he was concerned that Gen. David Petraeus "may not be in touch with what is really going on in Iraq."
Reid also criticized Gen. Peter Pace, chairman of the Joint Chiefs of Staff, for not doing a better job running the war.
Gates announced last week that he would not recommend Pace be renominated, and on Friday Pace disclosed for the first time that he had turned down an offer to voluntarily retire and save face. He said that to quit during wartime would be letting down the troops.
Reid said Petraeus' recent comments about some progress in Iraqi markets and neighborhoods may be "just trying to make the president feel good."
Gates lashed back, saying, "I think calling attention to the fact that in some areas things are actually a little better and looking pretty good, while they're very difficult in other areas is not unrealistic."
He said the situation in Iraq is a mixed picture, but one that shows pockets of improvement in some neighborhoods. He cited an open amusement park and bustling marketplaces and coffee shops as proof the situation is improving in some places.
And he added that he believes Petraeus "has not pulled his punches at all in terms of the difficulty of the struggle in front of us, in terms of the obstacles to both reconciliation and greater security in both the Baghdad area and Iraq as a whole."
He said he had "every confidence in General Petraeus, and also in his ability and willingness to call it like he sees it."
Still, as Gates landed there was a citywide clampdown in Baghdad, in an effort to hold off a backlash of Shiite attacks in retribution for the bombing of an important shrine north of the city.
The military also announced the and the crash of an Air Force fighter jet.
The additional five U.S. combat brigades that make up the recent U.S. troop buildup are now all in Iraq, as part of an increased effort to stabilize the violence in Baghdad.
Gates said he was meeting with military and political leaders to deliver the same message he did when he was here in April.
"That is our troops are buying them time to pursue reconciliation, that frankly we're disappointed with progress so far and hope that this most recent bombing by al Qaeda won't further disrupt or delay the process."
As he moves toward his September evaluation of the military buildup, Gates said he will look at progress in the smaller neighborhoods and tribal relationships, as well as how far the national government has moved on legislation, such as oil revenue sharing, and political reconciliation.
Military leaders have touted progress in the Anbar province since last fall when violence wracked the region. Now some tribal leaders have been working with troops to restore security.
Gates also said he thinks too much has been made of the administration's suggestion that the ongoing U.S. military presence in South Korea could be a model for the future in Iraq. He said the goal is to work with the Iraqis to establish a long-term relationship where the U.S. can continue to help them train and equip their forces.