As U.S. forces in Iraq reel from a rapidly expanding insurgency, Americans are beginning to ask whether we have stumbled into a Vietnam-style quagmire. It is appropriate to hesitate before making that comparison. Critics of U.S. military interventions have been too quick to invoke the Vietnam analogy in the past. We heard similar warnings about “another Vietnam” during the interventions in Somalia, Haiti, Bosnia, and Kosovo. In all of those cases, the warnings were — at the very least — overblown.

But this time the critics appear to be right. The breadth of the insurgency, the difficulty the United States is encountering in pacifying the country, the inability to tell friend from foe, and the weakness and unreliability of pro-American indigenous factions are eerily reminiscent of Vietnam. America seems to be in a fight that it cannot win — at least cannot win at any reasonable level of cost in terms of blood and treasure.

U.S. leaders now face a choice similar to the one Lyndon Johnson’s administration confronted in 1964 and early 1965. At that time, it was becoming evident that a limited U.S. military commitment was insufficient to defeat the communist forces in South Vietnam. Administration leaders faced a stark choice: withdraw American forces, even though Washington’s credibility throughout the world might be damaged, or escalate by sending in more troops. The Johnson administration ignored the advice of realist foreign policy experts, such as Hans Morgenthau and Walter Lippmann, and chose to escalate. It thereby transformed a foreign policy setback into a debacle.

The choice in Iraq is much the same. Voices advocating escalation can be heard already, including Sens. John McCain and Joseph Lieberman. In a narrow sense, their analysis is correct: The United States does not currently have enough troops in Iraq to control the deteriorating situation.

But escalation would be as unwise and futile as it was in Vietnam. A growing number of Iraqis-even those who originally were happy to see Saddam Hussein ousted — now view the United States as an alien, occupying power. The willingness of Shiites and Sunnis to bury their long-standing rivalry and cooperate in the latest insurgent attacks is an ominous sign. Worse, the occupation of Iraq has become a provocation to much of the Muslim world. We have overstayed our welcome in Iraq. Sending in more troops may dampen the current round of fighting, but it will not overcome those problems.

Admittedly, a rapid U.S. withdrawal from Iraq is not without its drawbacks. America’s credibility will take a hit, and radical Islamist forces will interpret the result as a victory for their side. Post-occupation Iraq could be a very ugly place, with a full-blown civil war a possibility. Those are all factors that advocates of the Iraq war should have considered before embarking on that mission. Opponents of the war warned that a U.S. intervention would create more instability, not less, in Iraq and throughout the region. Unfortunately, those warnings went unheeded, and we now face a choice of decidedly less than perfect options.

Advocates of staying the course blithely argue that we cannot “cut and run.” But a principle from the world of investing applies to wise and prudent foreign policy. Smart investors know that it is better to cut losses early rather than stubbornly hold on to an investment that has gone sour — much less pour more resources into such an investment. Those who defy that logic end up like the Enron and Worldcom investors who rode those stocks all the way to the bottom.

The U.S. mission in Iraq is an investment that has gone sour. We should cut our losses now, while they are relatively modest. If we don’t, we will likely be compelled to terminate the mission later under even less favorable circumstances. Moreover, by then we will have wasted tens of billions of dollars and thousands of American lives in a futile venture. A smart superpower should not make such a blunder.