(CNN) -- Iraq is important to U.S. security worldwide because it is "the central front of al Qaeda's global war of terror," Gen. David Petraeus said Wednesday.
Al Qaeda could use Iraq as a base to "export violence," Gen. David Petraeus said Wednesday.
"We don't know what would happen if al Qaeda had a sanctuary in Iraq from which they could presumably export violence, perhaps train others. We just don't know," Petraeus told a news conference in Washington.
The top U.S. commander in Iraq was clarifying an answer he gave to Sen. John Warner, R-Virginia, during a hearing before the Senate Armed Services Committee a day earlier.
Warner asked the general if U.S. military strategy in Iraq was making America safer.
"Sir, I don't know, actually. I haven't sat down and sorted it out in my own mind. What I have focused on and what I'm riveted on is how to accomplish the mission of the Multi-National Force-Iraq," Petraeus told Warner on Tuesday. Watch how Republicans challenged Petraeus »
Petraeus elaborated before the National Press Club on Wednesday.
If a U.S. pullout left Iraq to al Qaeda influence, Petraeus said, "would it be focused in the Levant, in the Magreb, back in Afghanistan, Western Europe, the United States? I don't know that."
Ryan Crocker, the U.S. ambassador to Iraq, went further.
"We have to assume that anywhere al Qaeda can find operating room, space, the ability to organize, to consolidate, they're going to use that to come after us," said the ambassador, who had testified side-by-side with Petraeus the past two days on Capitol Hill.
Petraeus said during the hearings Monday and Tuesday that the U.S. military would be able to pull about 30,000 troops from Iraq by July 2008. That would get U.S. troop strength back to pre-"surge" levels.
The "surge" began in January when President Bush ordered nearly 30,000 additional troops to Iraq in January as part of a campaign to secure Baghdad and its surrounding provinces.
Again on Wednesday, Petraeus would not say how long U.S. troops would be needed in Iraq.
Asked if a long-term security pact with Iraq would mean tens of thousands of U.S. troops would remain in Iraq for years, Petraeus said, "It is very, very difficult to project out much further beyond the horizon at this point in time, even just to mid-July of next year."
Crocker reiterated Wednesday that he believes Iraq will need U.S. help for the long haul.
"There are no shortcuts. ... there's just no switch to flip that's going to automatically move Iraq overnight into a situation of security and stability," the diplomat said. "It will be a long, hard grind. Right now, I think that grind is making progress." E-mail to a friend