Lance Cpl. Curtis M. Swenson, a 20-year-old Marine from Rochester, died April 2 in Afghanistan after his vehicle hit an improvised explosive device. While no one claimed responsibility, it's likely the bomb was planted by the Taliban, which the United States has spent billions of dollars -- and more than 1,000 lives -- trying to defeat.

Swenson's death came just hours after Afghan President Hamid Karzai, whose government the Minnesotan died defending, reportedly threatened: "If you and the international community pressure me more, I swear that I am going to join the Taliban."

We were against President Obama's decision to escalate involvement in Afghanistan for many reasons. Chief among them were worries over winning a war with an unreliable partner like Karzai, who has been accused of stuffing ballot boxes as well as his and his family's pockets. Indeed, the source of his frustration and outburst is American push-back against this corruption, as well as Karzai's insistence that he be able to pack with cronies an electoral commission charged with investigating alleged voting irregularities. But even our skepticism didn't imagine Karzai's cynicism and open consideration of supporting an enemy that he, and we, have vowed to vanquish.

Frustration with Karzai goes beyond his flirtation with the Taliban. Reportedly angry over an Obama administration snub, he invited Iranian President Mahmoud Ahmadinejad -- whom the United States and other responsible countries have been trying to isolate because of Iran's nascent nuclear program -- to Kabul, where Ahmadinejad delivered his latest screed against America.

Karzai's behavior is counterproductive at best and deadly at worst. In a battle that won't be won with arms but rather by winning hearts and minds, Karzai emboldens the Taliban and sends an inconsistent message to the very villagers our troops are trying to convince to side with the Afghan central government instead of local Taliban forces.

While galling, Karzai's push-back is consistent with the often-strained relationship between indigenous governments and western powers protecting them. A similar dynamic occurred with the United States and Vietnam.

How should Obama respond? As with nearly every aspect of the war, there are few options, all of them bad. Threatening to leave is tempting. But unless Obama is actually willing to pull out, it is empty rhetoric that will also embolden the Taliban and sap morale of NATO and Afghan troops.

Using the bully pulpit isn't working, either, as Karzai only seems to get the bully part.

Instead, Obama should be what Karzai is incapable, or unwilling, to be: strategic and rational. The diplomatic spat is hurting the war effort. The rhetoric needs to cool before it develops into a full-blown crisis.

This doesn't mean the Obama administration shouldn't keep up the pressure privately. And with the United States involved in so many ways in keeping Afghanistan functioning, from digging wells to building bridges, there are many ways to register displeasure and show that actions have consequences. If smaller steps are ineffective, the United States needs to turn up the heat even more until Karzai realizes the imperative of ending his erratic behavior.

Following a rational strategy is less satisfying than lashing out at the unreliable and ungrateful Karzai. But as commander in chief, the president must stay focused on the mission. Exacerbating the war of words hurts the war effort and puts more Marines like Swenson in even graver danger. While staying the course on policy, Obama needs to hit the right political notes, lest the diplomatic conflict result in the battlefield quagmire many have predicted.