Coalition forces were bearing down on Baghdad Thursday, with U.S. Special Operations forces operating inside the Iraqi capital and coalition troops preparing to seize Saddam International Airport on the outskirts of the city.

For the first time since the war began, the electricity went off in the city of 5 million shortly before 8 p.m. (noon EST). Loud explosions were heard on the city's outskirts for 15 minutes before the power went out.

Lead units of the multi-pronged U.S. assault force were approaching from two directions: Army troops were closing in from the southwest after crossing the Euphrates River, and Marine units were advancing from the southeast in a long column along the Tigris River.

• Map: The War in Iraq

"We are getting closer and closer," said Navy Capt. Frank Thorp, a Central Command spokesman. "We will be in Baghdad within a matter of hours from when we decide to go."

But the U.S. military warned that the war is far from over.

"There's apparently a little euphoria going through some that 'Hey, this is about over.'" Gen. Richard Myers, chairman of the Joint Chiefs of Staff, told Australian journalists Thursday. "I don't subscribe to that. I never have. Everytime I've talked about it, I've always said it's going to get harder and harder and harder the closer you get to the capital. And I will stick with that."

"We don't think that the fighting is over yet," Brig. Gen. Vincent Brooks said during a U.S. Central Command briefing. "There are still options that are open to the regime, including weapons of mass destruction. We take that very seriously."

Myers said Republican Guard divisions appear to be moving south to engage the coalition forces and are not heading into Baghdad for street-to-street fighting.

"They want to meet the advance, not fall back into Baghdad," Myers said. "That's what it looks like right now."

President Bush, in an address at Camp Lejeune in North Carolina, told the assembled troops:

"The course is set. We're on the advance. Our destination is Baghdad and we will accept nothing less than complete and final victory."

Bush traveled to the Marine base to comfort relatives of soldiers killed in Iraq. At least 13 of the Americans killed since the war started two weeks ago were from Camp Lejeune, and six more are missing.

One U.S. soldier was killed Thursday and several others were missing or injured in a possible friendly fire incident involving an F-15E fighter jet.

Earlier Thursday, at least six soldiers were killed when an American Black Hawk helicopter went down in Iraq. Central Command said it didn't believe enemy fire had downed the chopper. A Navy F/A-18 Hornet warplane was likely shot down by enemy fire; the fate of its pilot is unknown.

Special Operation teams have raided key regime locations, including Thar Thar Palace, about 56 miles outside Baghdad, which served as a residence for Saddam Hussein and his sons.

Navy Lt. Mark Kitchens said coalition forces "are beginning to see strong and credible signs that the Iraqi forces are being overwhelmed and will soon collapse."

"There is increasing evidence that the regime cannot control its forces or the Iraqi population in most of the country," Brooks added.

Iraqi Soldiers Shed Their Uniforms

As temperatures soared into the 90s Thursday, coalition forces swept through roads littered with black combat boots as Saddam's loyalists, hoping to avoid capture, shed their uniforms and switched to tribal robes. Many Iraqi units have quickly abandoned their positions and fled

But Iraqi authorities vowed to make a stand.

"God willing, we will teach the enemy lessons on the battlefield that it will not forget," said an officer identified as the commander of the Republican Guard's Baghdad Division.

U.S. officials said the Baghdad and Medina divisions of Saddam's Republican Guard had been destroyed, and the remaining four Guard units were moving to the south in an apparent effort to shore up Iraqi defenses.

"They are in a position from which there is no escape," said British forces spokesman Group Capt. Al Lockwood.

In the War Zone

Bombs shook the capital Thursday as Army and Marine armored columns took separate, converging paths toward the city from the south.

Central Command has information that Iraqi forces may plan "anonymous bombings" of Shiite neighborhoods in Baghdad, looking to blame coalition troops for these sabotage attacks.

Thousands of troops are within the so-called red zone -- an imaginary line near the capital where Iraqi use of weapons of mass destruction is most feared. Lead troops donned chemical protection suits.

The 7th Infantry crossed the Euphrates River from the south and west of Baghdad after fighting to hold the bridge at Musayyib, 35 miles south of the capital. The bridge was wired with explosives.

Scores of blown up Iraqi vehicles and dozens of dead bodies lined the roads where the Iraqis had built fighting positions.

In Kut, an Iraqi military town on the Tigris River, Marines were going building-to-building to battle Iraqi fighters. Three Marines were wounded.

Outside Kut, Marines opened fire on a military training academy, blowing a hole into a mosaic portrait of Saddam.

Residents said women and children had been sent out of the city in the past days and that pro-Saddam militias had taken young men away to force them to fight.

"They want to give us machine guns and make us fight. We are civilians, how can we fight?" said Kut resident Kasem Fasil. "Some people, they didn't want to fight and they killed them."

Fear of Chemical Attack

Other Kut residents said they're afraid Saddam's forces will unleash chemical weapons on Shiite Muslim towns like theirs.

At a Baath Party building flying Iraqi flags, a small group of men sat clustered in a grassy area around a woman dressed in a black chador and waving a white flag of surrender.

Many groups of Iraqis sat down by the roadside, waving and smiling at the Marines to show they were not combatants.

Brooks said that Ayatollah Sayyid Ali al-Husseini al-Sistani, a Shiite leader who had been under house arrest in Iraq, had issued a fatwa urging Iraqis to remain calm and not to interfere with coalition troops.

"We are seeing evidence of other religious leaders who have had enough of this regime," Brooks said.

Senior Defense officials told Fox News that a number of Islamic clerics in Iraq will issue statements or religious edicts supporting coalition forces.

"In coming days we know several clerics will issue statements of support for coalition operations," one official said. "We expect to see a lot of them."

The Marines found a cache of untouched chemical weapons protection suits at one Iraqi bunker.

Evidence has been found in the Kurdish-controlled regions of northern Iraq that the Islamic militant group Ansar al-Islam was working on three types of chlorine gas and ricin and has ties to Al Qaeda, U.S. officials told Fox News.

Officials said that between 75 and 150 Al Qaeda members have been captured or killed in northern Iraq in recent days.

Black Hawk Down

Despite earlier reports that an Army Black Hawk helicopter was downed by small-arms fire near Karbala, Brooks said it probably wasn't downed by enemy fire.

"The investigation into that is ongoing," he said.

At least six soldiers were reportedly killed and four were wounded and rescued. It was the first American fighter jet shot down during the war. A rescue team was deployed.

The U.S. military also announced that a Marine died Monday in a power line accident in Nasiriyah. The soldier was manning a rifle on top of a 7-ton truck when the vehicle passed under low hanging power lines.

Fox News' Bret Baier, Carl Cameron, Major Garrett, Mike Tobin and The Associated Press contributed to this report.