Iraqi forces are capable of defending their country from insurgency despite the two days of violence, a spokesman for U.S. forces in Iraq said. U.S. Army Maj. Gen. Jeffrey Buchanan in a USA Today editorial board interview said the deadly terrorist attacks this week that killed at least 77 people wouldn't threaten the Iraqi government, despite some military experts urging U.S. troops to stay in the country beyond a Dec. 31 withdrawal date, USA Today reported Wednesday. "I think the Iraqi government understands the threat that both al-Qaida poses and that these militant groups pose and has the ability to defeat them," Buchanan said. "Defeating any of those is going to take consistent pressure on all parts of their networks for a long time." Despite the attacks, al-Qaida has become "very isolated and very degraded," Buchanan said. "The Iraqi security forces have had the lead for security since last summer and have been doing a capable job," he told USA Today. Critics maintain Iraqi security forces aren't prepared to provide the security required by a sovereign nation and withdrawing all U.S. troops by the end of 2011 per the Obama administration's commitment would be a mistake. "The Iraqi security forces are better and more capable than they have been, but I don't think they're capable of addressing an opposing force with any capability," said Stephanie Sanok, who helped develop the withdrawal plan when she was a State Department employee at the U.S. Embassy in Baghdad (2008-09). "They cannot repel external threats to Iraq." Tom Donnelly, director of the Center for Defense Studies at the conservative American Enterprise Institute, said at least three U.S. brigades would be needed to keep peace between Kurds and Arabs in northern Iraq and to maintain security in Baghdad and in the south.