KABUL — The senior commander for Special Operations forces in Afghanistan has suspended training for all new Afghan recruits until the more than 27,000 Afghan troops working with his command can be re-vetted for ties to the insurgency.

The move comes as NATO officials struggle to stem the tide of attacks on NATO forces by their Afghan colleagues. The attacks, which have killed 45 troops this year, have forced NATO officials to acknowledge a painful truth: Many of the incidents might have been prevented if existing security measures had been applied correctly.

But numerous military guidelines were not followed — by Afghans or Americans — because of concerns that they might slow the growth of the Afghan army and police, according to NATO officials.

Special Operations officials said that the current process for vetting recruits is effective but that a lack of follow-up has allowed Afghan troops who fell under the sway of the insurgency or grew disillusioned with the Afghan government to remain in the force.

“We have a very good vetting process,” a senior Special Operations official said. “What we learned is that you just can’t take it for granted. We probably should have had a mechanism to follow up with recruits from the beginning.”

In other instances, the vetting process for Afghan soldiers and police was never properly implemented, and NATO officials say they knew it. But they looked the other way, worried that extensive background checks could hinder the recruitment process. Also ignored were requirements that Afghans display proper credentials while on base.

“Everyone admits there was a lot of international pressure to grow these forces, and the vetting of these individuals was cast aside as an inhibitor,” said a U.S. official who, like other officials, spoke on the condition of anonymity because he was not authorized to speak publicly about the issue.

The move last week by Maj. Gen. Tony Thomas, who oversees Special Operations forces in Afghanistan,to suspend the training 1,000 new recruits followed the Aug. 17 shooting of two American Special Forces members by a new Afghan Local Police recruit at a small outpost in western Afghanistan.

The local police initiative places Special Forces teams in remote villages where they work with Afghan elders and government officials to help villagers defend themselves against insurgent attacks and intimidation. U.S. officials have touted the program, which numbers about 16,000 Afghans, as a critical way to spread security and the influence of the Afghan government to remote areas of the country where the Taliban have found haven.

But the program, which is slated to double in size to about 30,000 Afghans, also carries risks for U.S. troops. “We’re living with the Afghans,” said a second senior Special Operations official. “We can’t afford to take any chances with vetting.”

Since the program began in 2010, there have been three instances of Afghan Local Police recruits turning their guns on their American counterparts.