Iraq's military is in sad shape and essentially leaderless after two weeks of attacks from the air and the ground, Pentagon officials say.

"What strikes me is what seems to be a very poorly directed campaign on the Iraqi side," said Marine Corps Gen. Peter Pace, vice chairman of the Joint Chiefs of Staff. "Their execution on the battlefield has really been sad, from the standpoint of military execution."

U.S. tanks and armored vehicles entered Baghdad Saturday on what military officials called reconnaissance probes into the capital. U.S. Army units worked to consolidate their hold on the newly renamed Baghdad International Airport southwest of the city, while Marine forces advanced to the southeastern outskirts.

"We have substantial forces now moving into the city," said Navy Capt. Frank Thorp, a U.S. Central Command spokesman.

The pincer movement was meant to isolate Baghdad, said Air Force Capt. Dani Burrows, a spokesman for U.S. Central Command in Qatar.

"They're pretty much cut off in all directions," she said. "Pretty much what you've got here is a choke hold around Baghdad."

In a statement read on satellite television, the Iraqi military said a "valiant force" of Iraqi fighters turned back the Americans as they tried to move into the capital from the south. "We were able to chop off their rotten heads," the statement said.

Though U.S. troops were not immediately on the northern edges of Baghdad, Burrows said Iraqi lines of flight were cut off in that direction. No substantial American force was known to be on the city's northern or eastern outskirts on Friday.

Pentagon officials said the idea was to create a loose cordon around Baghdad, letting civilians leave and humanitarian aid enter, as special forces and regular troops went after Saddam Hussein's centers of power. It's a strategy meant to avoid much of the vicious street-to-street fighting the Iraqis say they want to inflict on American troops.

The Pentagon's No. 2 general said that while the battle's front lines might be somewhat stationary, raids from the air and ground will reach into the city.

"It's really a matter of timing between our air power and our ground power," Pace said in an AP Broadcast interview. "There's not going to be a waiting period. We'll continue to take the fight to the enemy in the air and on the ground."

Pace said whether Saddam was alive or dead was irrelevant.

"Either he's alive, and giving really bad direction to his armed forces, or he's dead and they're making things up as they go," Pace said.

U.S. special operations forces have played a bigger role in Iraq than in any war in recent history, a senior U.S. military officer said.

"As a percentage of (overall war) effort they are unprecedented for a war that also has a conventional part to it," Army Maj. Gen. Stanley McChrystal told a Pentagon news conference.

Another senior official, speaking on condition of anonymity, said more than 10,000 special operations troops were involved in Iraq -- the largest number for any U.S. war since Vietnam.

McChrystal said special operations forces were in all areas of Iraq, including in unspecified cities where they were assisting anti-government Shiite Muslims. They get far less publicity than conventional forces because of the secretive nature of their missions, which include sabotage and reconnaissance.

They would almost certainly play a role in wresting away control of Baghdad, now that Army and Marine troops have closed to within several miles of the Iraqi capital. Among their targets may be members of the regime, including Saddam.

Unconventional warriors are used in every conflict, but in Iraq they are particularly important because of threats like possible Scud missile attacks on Israel or other neighboring countries. Special operations teams in Iraq's western desert have been attacking airfields, command posts and suspected chemical and biological weapons sites, McChrystal said.

Conventional forces are the Marines, Army infantry, armor, air defense and artillery units; Navy ships and warplanes and Air Force bombers and fighters. Special operations forces are Army Special Forces and Rangers, Navy SEALs and Air Force special operators.

Victoria Clarke, spokeswoman for Defense Secretary Donald H. Rumsfeld, would not offer even a rough estimate of the number of special operations forces inside Iraq.

Another official, speaking on condition of anonymity, said some of these forces were moving in and out of Iraq from unspecified countries elsewhere in the Persian Gulf region.

"It's probably the most effective and the widest use of special operations forces in recent history, clearly," McChrystal said.

The total number of U.S. forces of all kinds inside Iraq is believed to be about 100,000.

Special operations forces in northern Iraq were working with rebel Kurds to assist them in attacks against Iraqi government forces and to lay the groundwork for Kurdish participation in a new postwar national government. They also enabled the safe arrival of the Army's 173rd Airborne Brigade.

Those in the north also were putting pressure on the remaining Iraqi units north of Saddam's hometown of Tikrit, one official said. With supply and communications lines to Baghdad almost completely severed, those Iraqi forces were not expected to hold out for long, he said.