The commander of US forces in Iraq told Congress on Monday he envisions the withdrawal of roughly 30,000 troops from the country by the middle of 2008, beginning with a Marine contingent later this month. In long-awaited testimony, Gen. David Petraeus said buildup in US troops over recent months had met its military objectives "in large measure." As a result, he told a congressional hearing and a nationwide television audience, "I believe that we will be able to reduce our forces to the pre-surge level... by next summer without jeopardizing the security gains we have fought so hard to achieve." Petraeus's high-profile appearance at an unusual joint hearing of two congressional committees was seen as a crucial moment as the United States looks to the future of its troubled involvement in Iraq. Petraeus is widely admired by Democrats and Republicans alike and the White House has looked to him to give a boost to its Iraq policies at a time that President George W. Bush's popularity as sagging, mostly because of his handling of the war. It also comes as Iraq has been a focal point of the November 2008 elections, with Democrats hoping to use opposition to the war to win control of the White House and expand their majorities in both chambers of Congress. Democrats generally favor more, and faster troop withdrawals. So far, Republicans have been generally willing to stick with Bush, who has argued insistently against a withdrawal deadline, even though Bush's handling of the war has become increasingly unpopular with Americans. Testifying in a uniform bearing four general's stars and a chest full of medals, Petraeus said he had already provided his views to the military chain of command. Rebutting charges that he was merely doing the White House's bidding, he said firmly, "I wrote this testimony myself. It has not been cleared by nor shared with anyone in the Pentagon, the White House or the Congress." Petraeus said that a unit of about 2,000 Marines will depart Iraq later this month, beginning a draw down that would be followed in mid-December with the departure of an Army brigade numbering 3,500 to 4,000 soldiers. After that, another four brigades would be withdrawn by July 2008, he said. That would leave the United States with about 130,000 troops in Iraq, roughly the number last winter when Bush decided to dispatch additional forces. Petraeus said a decision about further reductions would be made next March. While he focused his remarks mostly on military matters, he also noted the failure thus far of the Iraq government to take the actions needed to stabilize the country for the long term. "Lack of adequate governmental capacity, lingering sectarian mistrust, and various forms of corruption add to Iraq's challenges," he said. Using charts and graphs to illustrate his points, Petraeus conceded that the military gains have been uneven in the months since Bush ordered the buildup last winter. But he also said that there has been an overall decline in violence and said, "the level of security incidents has declined in eight of the past 12 weeks, with the level of incidents in the past two weeks the lowest since June of 2006." Petraeus also said the Iraqi military is slowly gaining competence and gradually "taking on more responsibility for their security." He cited Anbar province as an example of Iraqis turning against terrorists, adding, "we are seeing similar actions in other locations as well." Bush and his political allies have worked forcefully in recent weeks to shore up Republican support. One organization with ties to the administration has spent millions on television advertisements, and Bush traveled to Anbar province last week to highlight improved security in the vast western stretches of Iraq. Bush also called Iraqi Prime Minister Nouri al-Maliki in the hours before Petraeus spoke, and is expected to deliver a nationwide address on the war in the next few days. Despite the administration's efforts, fresh polls reflected significant public opposition to the war. A USA Today-Gallup poll taken in the past few days found that 60 percent of those surveyed favor setting a timetable for removing troops. Only 35 percent favor keeping the troops in Iraq until the situation improves. Petraeus and Ambassador Ryan Crocker were the only witnesses at a nationally televised hearing punctuated by numerous protests by anti-war demonstrators in the audience. Over and over, Rep. Ike Skelton, the Democrat presiding, ordered police to remove the demonstrators. "This is intolerable," he said at one point. Skelton and fellow lawmakers spoke first, as is customary in Congress, and Petraeus listened to more than 45 minutes of political rhetoric. His testimony was delayed another 10 minutes by a malfunctioning microphone, but when he began to speak, the lawmakers arrayed across from him listened intently. Crocker followed Petraeus to the microphone. The veteran diplomat said he could "not guarantee success," in Iraq. But he said he believes "it is attainable" and any significant shift away from the current strategy would embolden Iraq and al-Qaida despite difficulties with the Iraqi government. Crocker employed some of the most stark rhetoric of the hearing, when he bluntly said al-Qaida had "overplayed its hand" in Anbar province. "Anbaris began to reject its excesses, be they beheading schoolchildren or cutting off people's fingers for smoking," he said. The war, in its fifth year, has claimed the lives of more than 3,700 US troops and tens of thousands of Iraqis.