KABUL — Afghan officials say they have launched an expanded effort to spy on their own police and army recruits, an acknowledgment that previous measures designed to reduce insurgent infiltration in the country’s security services have failed.

The steps come amid a spate of “insider’’ attacks that have shaken the US-Afghan military partnership during a stage of the war that hinges on close partnership between the two forces.

Nine US troops have been killed by their Afghan counterparts in the past 12 days, and 40 coalition service members have died in insider attacks so far this year.

President Obama, in his most extensive comments to date on the issue, said Monday that his administration is ‘‘deeply concerned about this, from top to bottom.’’

The Afghan measures include the deployment of dozens of undercover intelligence officers to Afghan security units nationwide, increased surveillance of phone calls between Afghan troops and their families, and a ban on cellphone use among new recruits to give them fewer opportunities to contact the insurgency, Afghan officials say.

The initiatives appear aimed at addressing US criticism that the Afghan security forces are not doing enough to ferret out insurgents within their ranks. The chairman of the Joint Chiefs of Staff, Army General Martin Dempsey, was in Kabul on Monday for consultations on the matter, and Obama said he would soon be ‘‘reaching out’’ to President Hamid Karzai of Afghanistan.

‘‘Soldiers must feel that they are under the full surveillance of their leadership at all levels,’’ said the Afghan army chief of staff, General Sher Mohammad Karimi, in an interview after meeting with Dempsey and other US commanders. ‘‘Initially, it will have a negative impact on morale, but we have to do something. We have to look seriously at every individual.’’

NATO has taken steps in recent days to try to limit the attacks, which the Taliban leader Mohammad Omar has described as an integral part of his group’s strategy.

Across Afghanistan, service members have been asked to keep their weapons loaded at all times, according to coalition officials. NATO has also activated an existing program, dubbed the ‘‘Guardian Angels,’’ in which coalition troops enter meetings with Afghan officials prepared to quell an insider attack if one should occur.

Obama said US forces already are ‘‘seeing some success when it comes to better counterintelligence, making sure that the vetting process for Afghan troops is stronger.’’ But, he added, ‘‘obviously, we’re going to have to do more.’’

‘‘We are transitioning to Afghan security, and for us to train them effectively we are in much closer contact — our troops are in much closer contact with Afghan troops on an ongoing basis,’’ Obama said. ‘‘Part of what we’ve got to do is to make sure that this model works but it doesn’t make our guys more vulnerable.’’

Insider attacks are a relatively new aspect of the war, having emerged as a major problem for the United States and its allies only in the past several years.

Not all attacks have been the result of insurgent infiltration, and NATO officials have said that most stem from personal disputes. Afghan military officials say they have asked their US and other NATO counterparts to better educate their troops in local traditions and culture to help reduce the potential for conflict.

There have been more deaths from insider attacks in 2012 than in any other year of the war, and they have accounted for 13 percent of all NATO fatalities this year.

In the latest such attack, two Afghan police officers turned their weapons on US troops in Kandahar Province Sunday, killing an American service member, officials said. That attack happened in Kandahar’s Spin Boldak district near the border with Pakistan. The victim was a member of a US military advisory team working with the Afghan police there.

As US troops begin to withdraw, the attacks threaten to upend plans for a transition from foreign to Afghan control of security that will require tight choreography between the two forces.

But the new Afghan measures carry their own peril, with the potential to further alienate rank-and-file troops and would-be recruits at a time when the government is struggling to build loyalty.

Afghan officials say that in all, 176 intelligence officers were assigned to army battalions last week and that most will remain undercover. They join hundreds of others who are tasked with spotting wayward troops before they carry out ‘‘green-on-blue’’ attacks.

Karimi said Afghanistan would also reinforce a vetting procedure that had never been properly employed, allowing cursory or no background checks for new recruits.

A number of the attacks this year were carried out by individuals who faced little scrutiny in getting access to joint US and Afghan bases.

This month, an unvetted 15-year-old ‘‘tea boy’’ who had been living on a police base in Helmand Province killed three US Marines while they exercised.

‘‘We had a policy for recruiting from Day One, but it hasn’t been implemented. We needed too many people,’’ Karimi said. ‘‘When you need 12,000 people each month — it’s a number so high that we couldn’t implement the policy,’’

Now that the security forces are approaching their targeted recruitment levels, officials said, they can concentrate on ensuring that the right soldiers and police have entered the ranks. That means paying close attention to what they do after enlisting.

‘‘Whenever a new recruit goes on leave, we have reconnaissance following that person to make sure he doesn’t pose a threat,’’ said Major General Abdul Hamid, the top Afghan army official in Kandahar.

The Afghan efforts represent an expansion of earlier attempts to curb insider killings. Earlier this year, for instance, soldiers were forced to move their families back from Pakistan or quit their jobs. Many infiltrators are believed to have received training from insurgent groups in Pakistan.

Karimi briefed Dempsey and General John Allen, the top US commander in Afghanistan, on Monday on Afghanistan’s plans for the expanded counterintelligence measures.