A wave of soldiers and steel, the American-led ground force in Iraq rolled toward Baghdad Friday, meeting some resistance, taking some casualties. There could be plenty more obstacles on the way, the Pentagon's top general said.

Troops already had penetrated at least a third of the way toward Baghdad.

"Clearly, we're moving toward our objectives, though we must not get too comfortable," said Air Force Gen. Richard Myers, chairman of the Joint Chiefs of Staff.

"We're basically on our plan and moving toward Baghdad, but there are still many unknowns out there."

The ground advance into Iraq appeared to be moving faster than planned, with some units arriving at locations ahead of when commanders had told accompanying journalists they would.

The Army's 3rd Infantry Division moved its convoy of thousands of tanks, fighting vehicles and other heavy equipment quickly in the desert west of the Euphrates River, avoiding populated areas.

On the east, U.S. and British forces seized the port city of Umm Qasr and the Al Faw peninsula, moved through the southern Iraqi oil fields and secured oil industry equipment along Al Faw waterways.

"We've had sporadic resistance," Myers said, noting there were tank battles but calling them "generally limited."

Troops took the border town of Safwan without firing a shot and were welcomed by the townspeople.

Also along the way to Baghdad, forces came upon large numbers of abandoned Iraqi tanks and weapons, a defense official said.

Strike planes from U.S. aircraft carriers as well as Cobra and Apache attack helicopters hit military targets and gave ground troops air support to ease the drive.

Still, one official cautioned, coalition forces are not expecting such light resistance to continue. The American forces hadn't yet encountered the best among Iraq's forces -- the Republican Guard. Officials said there is one division to the south.

And the question of how much of a fight the invading force would encounter at Baghdad also remained a worry. Saddam Hussein has encircled the city with other Guard troops.

There were 14 coalition deaths as of Friday afternoon.

One U.S. Marine was shot as his company advanced on a burning oil pump station in Iraq's Rumeila oil field, the second died in the battle for Umm Qasr.

Eight British and four U.S. Marines died when their CH-46 Sea Knight helicopter crashed and burned in an accident about nine miles south of Umm Qasr.

Sources inside and outside the military had predicted the drive to Baghdad could be done in as little as three or four days, depending on what obstacles Iraqi forces threw in their way.

"If they had used chemical weapons at this point, that would have affected the timing," Myers said Friday.

How long to Baghdad? British military spokesman Capt. Al Lockwood said, "If I was a betting man, and I'm not, I would say hopefully within the next three or four days."

Some prewar fears have not yet come true. For instance, some feared mass surrenders could bog down coalition troops. Military officials had said they were expecting 270,000 Iraqis -- or more than half the Iraqi army -- to lay down their arms. So far Friday thousands had.

Officials also feared Iraqi forces would blow up dams and bridges -- the former bringing massive flooding, and the latter slowing water crossings by forcing troops to use bridging equipment.

At the press conference with Myers, Defense Secretary Donald H. Rumsfeld repeated his warnings to Iraqis who might use such tactics.

"Those who carry out such orders will be found and will be punished," he said.