The bombing of the U.N. headquarters building in Baghdad is being viewed as one of the most serious threats yet to the U.S.-led effort to restore order in Iraq.
Defense Secretary Donald Rumsfeld appears undaunted by this week's bloody bomb attack on the United Nations headquarters in Baghdad.
Speaking during a visit to Colombia, Mr. Rumsfeld insisted the United States and its coalition partners "will not be dissuaded nor deterred" in helping Iraqis establish a new, representative government to replace the regime of deposed dictator Saddam Hussein.
But some defense officials back at the Pentagon are now sounding significantly less confident than their boss.
Speaking on condition of anonymity, one senior military commander said he believes the only sure way to restore stability in Iraq is a long-term U.S.-led military occupation, perhaps decades-long. And he said that is something that is probably politically unacceptable to the American people, especially with the next presidential election campaign already getting under way.
A second key ingredient to restoring stability is the development of more Iraqi security forces, but this senior official said that is not something that can be accomplished overnight.
Still, some analysts say it is now evident that the bombing of lightly-guarded, so-called "soft targets" like the U.N. headquarters, the Jordanian embassy in Baghdad and Iraqi oil and water pipelines are intended to show U.S. forces cannot restore order.
They say targeting the United Nations, in particular, could be aimed at undermining U.S. efforts to win more international participation in postwar Iraq. Targeting the country's infrastructure could be intended to undermine Iraqi confidence that the United States and its allies can get the restoration job done.
Defense officials said they still have no idea who is behind these latest attacks.
But suspicion has already fallen on terrorist groups including Ansar al-Islam, linked by U.S. intelligence officials to al-Qaida.
In addition, U.S. authorities now concede more foreign fighters are pouring into Iraq, which they fear has become what one analyst calls a "magnet" for al-Qaida terrorist types.
Pentagon officials say they do not believe the attacks and the instability will be eliminated anytime soon.
But for the moment, they say there is no sign of any support within the Bush administration for increasing the size of the U.S. military presence in Iraq.
There are currently over 140,000 U.S. troops in the country. In addition, there are over 24,000 soldiers from other countries.