The recent string of “green-on-blue” (Afghan on US/Coalition troops) attacks in Afghanistan are cause for real worry: Not only might the Coalition’s vital mission to provide security training to the Afghan police and army be in trouble, but the country’s entire future might be in question, too.

Without the high-quality training the Afghan security forces desperately will need after Coalition forces leave in 2014 (or maybe sooner), it’s possible Afghanistan will once again fall to the likes of the Taliban.

And that’s exactly what the Taliban, the Haqqani network, al Qaeda — and maybe others — want.

What better way to achieve that goal than to cowardly go after the brave men and women who have the capacity to give the people of Afghanistan a chance for a secure future, free from an Islamist extremist stranglehold?

We’ve lost nearly 10 brave Americans to attacks by “friendlies” in just the past two weeks. There have been some 30 attacks on Coalition forces this year, causing nearly 40 fatalities.

That’s a treble increase in “insider” attacks over last year.

The trend line clearly isn’t good — and the effects are widespread.

First, these attacks have a chilling effect on our troops’ morale.They also shake the home front here and in other Coalition countries, putting pressure on the allies to bring their troops home from Afghanistan as soon as possible.

Keep in mind, too, that the fact that America is in all-out campaign mode for the fall elections hasn’t been lost on the insurgents, who hope to hasten a US retreat by going after public opinion here.

These attacks also undermine the trust that is critical between military trainer and student.How can trainers give the best training possible when they have to be concerned that the student might turn a weapon on them?

Equally troubling is the trust that is in jeopardy in the field where US and Afghan soldiers are patrolling together.

In a foxhole or on a foot patrol, you need to know that your fellow soldiers (Afghan or otherwise) are able — and willing — to get your “six.”

Sadly, our brave troops are now more worried about Afghans putting a knife in their backs than Afghans watching their backs. This anxiety will only compound as US forces complete a phased draw down this fall, on the glide path to a full withdrawal by 2014.

Finally, not only do these attacks hinder the training of government security forces, which will battle the Taliban and its allies, they also undermine confidence in Kabul, which might encourage Afghans to shift their allegiance to the insurgents.

And now consider this: Despite efforts by Coalition forces and the Afghan government to combat the violence through better screening, vetting, monitoring and counterintelligence, this isn’t going to be an easy problem to fix.

The Taliban, the Haqqanis and al Qaeda will continue to look for willing recruits to do their dirty work, developing “penetrations” of the Afghan army and police force to turn on their mentors and trainers.

The insurgents may corrupt or coerce Afghans into becoming attackers, too. And they’ll hone their propaganda to aggravate cultural differences between Coalition and Afghan security forces in hopes of inciting violence.

The green-on-blue attacks highlight the growing challenges that face our work in Afghanistan, including IEDs, assassinations of government officials, suicide bombings and Afghan concerns about being abandoned.

Now would be an ideal time for presidential leadership on Afghanistan to ensure the success of our mission there — especially preventing the return of the Taliban to power and the revival of al Qaeda.

Peter Brookes is a Heritage Foundation senior fellow and a former deputy assistant secretary of defense.