— Word from The White House is that the U.S. and Afghan President Hamid Karzai are in the process of working out details to some important agreements for that country's security. Starting in the spring (as opposed to mid-year as previously planned), Afghanistan will take the lead role in its defense and the U.S. mission will consist of training, advising and assisting.

"It will be a historic moment," President Barack Obama declared Friday when he announced the new plan.

But the future of that country is far from secure. There is much to be concerned about, in fact.

Start with troop levels. The U.S. now has 66,000 troops there. After the combat mission ends in 2014, Obama will consider military options that give him anywhere from 6,000 to 15,000 soldiers to remain there. Or maybe all our troops will be brought home. Last week, White House deputy national security adviser Ben Rhodes said the administration isn't ruling out leaving no troops in Afghanistan at all.

This "zero option" may be intended as a negotiating tactic with Karzai, who has so far been reluctant to grant legal immunity from prosecution under Afghan law for U.S. troops that remain behind. But it's worrisome to even consider such an idea publicly.

It is true that American support for the U.S. Afghan presence is slipping, but that should not be the basis for reducing our resolve. Our stated objective remains to make Afghanistan safe from the Taliban, and yet we do not yet know whether Afghanistan can succeed in that effort without our help. Many doubt Karzai's staying power in the event of a lesser U.S. presence. Many doubt whether the current Afghan government can maintain legitimacy with its own people over the long haul.

Certainly, Afghan fighters will need to be much improved from what we've seen from them. Corruption continues to be a problem. The Afghans have resented our leadership role as much as they've embraced it, and further complicating the situation is the fact that, although fewer than 100 al-Qaida fighters are reportedly in Afghanistan now, many more are just across the border in Pakistan.

Our Afghan enemies welcome any hint that our commitment might lessen. It inspires them as much as it makes our Afghan partners nervous.

Clearly, the U.S. has tied up a great deal of capital in Afghanistan, in lives and in funds. We must ensure that our long-term interests in that the country remain stable and able to blunt a Taliban resurgence are met.

So rather than listen to trial balloons from The White House about reducing our commitment to zero troops, we should reiterate and strengthen the strategic commitment we share with the Karzai government. And we should make it clear to our enemies, who wish us to abandon that cause, that our resolve has not weakened.