WASHINGTON, 30 March 2003 — With a single comment made while visiting hard-pressed American troops in central Iraq, Lt. Gen. William S. Wallace, commander of all US Army forces in the Gulf, has forced into the open a question his superiors have been trying to sidestep since the war began: How long will it last?

“The enemy we’re fighting is different from the enemy we war-gamed against because of these paramilitary forces. We knew they were here, but we did not know how they would fight,’’ Wallace said during a visit Thursday to a command post of the 101st Airborne.

Did that mean the war would run longer than expected? “It’s beginning to look that way,’’ he said.

As reports of Wallace’s comments spread through Washington, D.C., Friday, the White House moved quickly to scotch any suggestion that the Pentagon’s battle plan might be in trouble and that the war might thus run longer than expected.

“The president has faith in the plan. He believes that the plan is on track, it is on progress, it is working,’’ said White House Press Secretary Ari Fleischer. Meantime, US Defense Secretary Donald H. Rumsfeld and Gen. Richard Myers, chairman of the Joint Chiefs of Staff, pointed out that the plan had been vetted with the whole panoply of senior US commanders.

“Overall, our plans are on track,’’ Myers said.

In other circumstances, a perhaps overly candid assessment by one general might have passed unnoticed. But Wallace’s comments hit like a thunderclap because they spoke volumes about the tensions simmering beneath the surface of the war in Iraq.

In part, the tensions arise from the strains of a 72-hour period in which the US and UK forces suddenly seemed to have stumbled into a sea of troubles. Fedayeen paramilitary fighters kept up bloody raids on lengthening allied supply lines. Iraqi troops refused to crumble. The army’s tank-killing Apache helicopters were turned back by low-tech ground fire. And Saddam Hussein remained in power.

The flare-up over Wallace’s candor brought to the surface the lingering unease among some US officers and outside analysts over the fact that civilian leaders in the Pentagon sent US forces into Iraq with a substantially smaller force than military planners originally envisioned.

And the pell-mell advance of US, UK forces — some 300 miles in less than a week — has stretched supply lines and support systems far beyond anything logistics officers normally train for.

“This is a very bold, audacious plan, but it is poorly resourced,’’ complained a former field commander in the 1991 Gulf War. “They need operational depth and they don’t have it.’’

Despite such tensions, both senior army officers and many outside analysts say the paramilitary attacks and other challenges are relatively minor when compared to what has been achieved. And many predict that — weather permitting — it might take no more than another month to destroy Saddam Hussein’s Republican Guard, Special Republican Guard and other organized military forces.

“Three or four weeks, if we have to take the city down,’’ said Andrew Berdy, a retired army colonel who commanded US troops around An Nassiriyah in 1991, referring to the possibility that the final push might require a direct assault on Baghdad.

Saddam’s organized forces might be overcome more quickly, Berdy said, if they remain arrayed as they are now — some miles outside the capital.

“The question is whether we can isolate the Republican Guard outside the city. I hope we can,’’ he said, “because as soon as they move and are out in the open, we can nail them.’’

“There is still a lot of combat power in the region that has not yet engaged with Iraqi combat forces,’’ agreed Richard Hart Sinnreich, former director of the Army School of Advanced Military Studies.

While attacks by Fedayeen and some units of the regular Iraqi Army have inflicted painful casualties and forced adjustments by US commanders, Sinnreich said, in military terms “they are pin pricks.’’

Saddam’s defensive strategy, however, has caused problems for US, UK commanders or forced them to adjust their own tactics.

“There is no question they didn’t anticipate the Fedayeen,’’ said William M. Arkin, a military analyst at the Johns Hopkins School of Advanced International Studies, “or that they overestimated ‘shock and awe’ and the degree to which US, UK forces would be welcomed as liberators.’’

Still, the goal was to get to the outskirts of Baghdad quickly, he added, and that has been accomplished in one week. “My guess is three weeks,’’ he said of the time it will take to crush Saddam’s organized forces.