Al Qaeda in Iraq is "off balance but still dangerous," but the decision of sectarian factions to drop their association to the terror network has greatly led to the decrease in violence there, the top commander in Iraq told FOX News.

Gen. David Petraeus and Ambassador Ryan Crocker are facing another grueling day of testimony in front of Capitol Hill lawmakers on Tuesday — the sixth anniversary of the Sept. 11, 2001, terror attacks — after appearing for six hours in front of a joint hearing of the House Armed Services and Foreign Affairs committees on Monday. They followed their first day of testimony with an exclusive hour-long appearance with FOX News.

The top military and diplomatic leaders agreed that progress is uneven but definitely noticeable.

"Al Qaeda is still the element in Iraq that carries out the most significant attacks, causes the most casualties" and tries to stir the ethno-sectarian violence, Petraeus said. On top of that, "Shia death squads" are still active, but their actions have been greatly reduced.

"There's still work to be done although the reduction (in violence) is substantial," he said.

Petraeus said the Golden Dome Mosque bombing in Samarra in February 2006 was an Al Qaeda operation that brought down much of the progress that had been achieved in Iraq since the toppling of dictator Saddam Hussein in May 2003.

After the bombing, sectarian violence began to grow, and climbed until mid-June of this year when the U.S. troop surge was completed. Since then, Petraeus said, the level of violence has again begun to come down, with the last two weeks being the most peaceful since June 2006.

Petraeus said a lot of that was due to the tribes and sheiks in different regions agreeing to work with the U.S. forces and throw off Al Qaeda.

"The tribes and the sheiks decided to say no more to Al Qaeda. They were tired of the indiscriminate violence, tired of the Taliban-like ideology and the other practices," he said. "They are Sunni Arabs rising up against a largely Sunni Arab Al Qaeda in Iraq."

Petraeus said "the jury is still out" on some segments of the national police, but the progress so far has led him to support continuing the mission, which both men called imperative to the region.

"The region and the international community have suffered for a long time from an Iraq that was basically a threat" under Saddam Hussein, Crocker said. He called Iraqi Prime Minister Nouri al-Maliki a man of courage and integrity who now should be given the chance to lead his countrymen out of the old mentality of repression and into a new era.

"The courage we saw, again, during the fighting in Karbala 10 days ago. Pretty messy situation. His immediate response was to organize a convoy, go down himself and lead from the front. He took charge of that operation within 12 hours of the first shots being fired. And that's the kind of thing that I think Iraqis respect," Crocker said.

In the interview, the two men revisited much of their testimony on Capitol Hill. They also defended themselves from claims that they were part of a dog and pony show being put on by the White House.

Both leaders repeated their statements from earlier in the day that they were the authors of their own testimony and were not being queued on what to say. Petraeus added that he stands by an op-ed he wrote in 2004 in which he said the U.S. Army was succeeding in helping the Iraqi army. He described the article as truth that was interrupted by Al Qaeda's Golden Dome Mosque bombing.

The two also said they believe in their mission.

"I think an enormous payoff is the fact that we may be able to defeat al Qaeda. Al Qaeda central, if you will, does regard Iraq as the central front in its War on Terror," Petraeus said. "The converse of that would be a, really, a huge lift for al Qaeda, and really, a shot of adrenaline to them."

"I think we have a prospect now of helping bring into being an Iraq that is the opposite, a source of stability and security in the region. And I think that's important," Crocker said.

Troop Reduction Plan Doesn't Impress Democratic Lawmakers

Earlier in the day, antiwar lawmakers did not appear moved by Petraeus' announcement that he's planning on ordering home one Marine unit from Iraq at month's end and another Army brigade in mid-December.

Petraeus predicted a drawdown of U.S. troops in Iraq by next summer to pre-surge levels, but he would not offer numbers beyond July.

"I believe that we will be able to reduce our force to the pre-surge level of brigade combat teams by next summer without jeopardizing the security gains that we've fought so hard to achieve," Petraeus told the joint hearing.

"Our experience in Iraq has repeatedly shown that projecting too far into the future is not just difficult, it can be misleading and even hazardous," Petraeus added.

Petraeus said the total number of troops to be withdrawn by next summer — one Marine expeditionary unit, two Marine battalions and five Army brigades in all — is a "substantial" withdrawal that would allow the remaining forces to continue operational and strategic considerations, including fighting off Al Qaeda in Iraq and Iranian "militia extremists."

The numbers didn't satisfy many Democratic lawmakers, several of whom described Petraeus' testimony to Congress as the work of the White House.

"We've heard a lot today about America's credibility. President Bush recently stated we should not have withdrawn our troops from Vietnam because of the great damage to America's credibility," said Rep. Robert Wexler of Florida.

"General, there are 58,195 names etched into the Vietnam war memorial. Twenty years from now, when we build the Iraq war memorial on the national mall, how many more men and women will have been sacrificed to protect our so-called credibility? How many more names will be added to the wall before we admit it is time to leave? How many more names, General?"

Petraeus responded that no one feels the loss of troops more than a commander. He added that a quick departure is not the best course for the region or the U.S. Al Qaeda in Iraq would regain its faltering foothold, and a premature withdrawal would leave instability in many areas that are now achieving sustainable security.

On the diplomatic track, Crocker told FOX News that he's trying to convince his Iranian counterpart — who is a member of the elite Quds military force that controls Iranian foreign policy — that it's not in Iran's interest to try to destabilize Iraq.

"I think you see a collision in Iran between their long- term strategic interests and their narrow tactical desires. Their narrow tactical desires I would define as trying to administer a defeat to the U.S. in Iraq. The problem they've got is that, if they are able to create circumstances that cause us to reconsider our commitment, the result is going to be a chaotic Iraq that, over the long run, could potentially be dangerous for them, as well," Crocker said.

The two leaders are likely to get another grilling on Tuesday, when they appear at separate hearings of the Armed Services and Foreign Relations Committees. Ahead of the appearance, the Senate Democratic Communications Center issued a press release repudiating Petraeus' testimony.

"Unfortunately, his remarks raise as many questions as answers," the release said.

Senate Majority Leader Harry Reid said in a statement that it's time to pull troops out of Iraq.

"U.S. national security requires that we truly and immediately change course in Iraq, so that America can more effectively dedicate our resources to other, more pressing challenges we face across the globe," he said. "Bin Laden remains at large and his terrorist organization has rebuilt its strength to pre-9/11 levels, Afghanistan’s stability is being undermined as the Taliban and narco-traffickers grow in strength, and Iran and other countries and groups pursue the acquisition of nuclear weapons technology."