Back in April, George W. Bush pledged a reconstruction program for Afghanistan on the order of the Marshall Plan.

Nothing of the kind happened, as U.S. efforts focused mainly on boosting warlords who might help chase down remnants of al-Qaeda. Rebuilding has barely started, and the lag has undermined the central government of Hamid Karzai.

Things have reached such a point that top U.S. military commander Gen. Richard Myers suggested last week that our forces might do better by switching from combat operations to “the reconstruction piece in Afghanistan.”

Which brings us back to the issue of “nation-building” – can we do it, should we, do we really want to? The disconnect between Bush rhetoric and reality in postwar Kabul doesn’t bode well for Iraq.

The nation-building responsibilities that will crash down on American shoulders if we enter Baghdad will make our Afghan problems look simple. There has been no shortage of administration rhetoric about what should happen in Iraq after “regime change.” But disagreements within the administration are sharp and public about what to do once Saddam is gone.

One school of thought, popular among key Pentagon civilians, has been aptly labeled “democratic imperialism” by the Brookings Institution’s Ivo Daalder. The democratic imperialists, including Deputy Defense Secretary Paul Wolfowitz, believe America can help build the first Arab democracy in Baghdad, which would then trigger a democratic chain reaction throughout the Mideast region.

Within this school of thought there are optimists and pessimists. The former think Iraqis have the talent and (oil) money to do most of the democracy-building themselves, and the U.S. wouldn’t have to keep many troops there. The pessimists believe democracy-building would require a long-term U.S. occupation with an American proconsul like Gen. Douglas MacArthur in post-World War II Japan.

Old-school realists like Secretary of Defense Donald Rumsfeld seem less interested in establishing democracy than getting rid of Saddam’s weapons of mass destruction – and stabilizing Iraqi oil fields. As for the State Department and the CIA, skeptics there believe prospects for Iraqi democracy are slim. But they fear that once the United States gets into Iraq we will be saddled with responsibility for an unholy mess.

These deep differences make it extremely difficult to fashion a coherent policy for The Day After. Both State and Defense Departments have teams beavering away at competing blueprints for the post-Saddam era, but there’s no single administration plan.

I doubt the United States has the will or wallet to keep tens of thousands of troops in Iraq for an indefinite occupation. Every Iraqi opposition leader I speak to tells me Iraqis would turn against any large-scale occupation that lasted more than a few months.

Yet anyone who imagines that Iraqis will easily come to agreement on a postwar government by themselves is dreaming. They face ethnic power struggles, tribal differences, and conflicts over oil. Moreover, Iraq’s neighbors may seek to intervene in its territory or politics.

Anything that resembles democracy as we know it is way off.

If we invade, however, we take on responsibility for fostering a new Iraqi government, whatever its nature. We also take on the responsibility of ensuring Iraq’s reconstruction. Keep in mind that Iraq’s needs, debts, and reparations obligations will far outstrip oil revenues for some time. United Nations support may guarantee some help with rebuilding, but the main burden will fall on the U.S. of A.

I haven’t yet heard any administration speeches that call for a Marshall plan for Baghdad and explain what it will require.

More disturbing, the divisions within our government over the shape of Iraq’s future reinforce splits within the Iraqi opposition. An conference of exiles is supposed to be held in Brussels late this month to demonstrate unity among Saddam’s opponents and start preparing for a post-Hussein government. Instead, the conference may split into two.

Officials of one group, the Iraqi National Congress, which is led by Ahmed Chalabi, who has strong support among Pentagon civilian officials, are threatening a boycott. Chalabi wants a broader conference to set up an interim government, which would be installed on the first piece of territory American troops take.

Key Kurdish and Shiite opposition groups charge that Chalabi wants to grab power, and has no support at home. Other Iraqi opposition figures say a transition government of technocrats is needed, paving the way for future elections.

The squabbles within the administration only strengthen the Iraqis’ disagreements. State and CIA reject the idea of an Iraqi transition government composed of exiles because they think the real Iraqi leadership will emerge from inside the country. Pentagon officials swear by Chalabi.

The reality: The Iraqi opposition has no Mandela, and Chalabi, for all his talent, cannot fill the bill. Unless the administration unifies itself, it can’t unify the Iraqi opposition or get it to produce a viable transition council.

So U.S. and allied forces will wind up running Iraq. They will take on the huge burden of godfathering elections. The president’s special assistant for Near East Affairs, Zalmay Khalilzad, has said this will probably happen.

George W. Bush will face a nation-building challenge more substantial than anything he promised for Afghanistan. If we bug out, the costs will be far more serious.

Is the American public ready for that?

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer.