Afghanistan is unable to adequately track personnel and pay within its police force despite more than 13 years and billions of dollars of outside assistance, a U.S. watchdog said Monday, highlighting concerns about security forces as the United States and other Western nations withdraw.

In a new audit report, the Office of the Special Inspector General for Afghanistan Reconstruction (SIGAR), an independent U.S. government body, said the United States, United Nations and NATO also bear responsibility for failing to resolve persistent weaknesses in the Afghan Interior Ministry’s management of police units across the country.

Now, as the Western presence in Afghanistan grows smaller, the ability of donor countries to exercise proper oversight will only diminish, SIGAR warned in its report.

“There is a significant risk that a large portion of the more than $300 million in annual U.S. government funding for [Afghan police] salaries will be wasted or abused” if the problems are not addressed, SIGAR said.

More than 13 years after the international mission in Afghanistan began, a reduced U.S. and NATO force is now focused on supporting Afghan police and soldiers in their fight against the Taliban. By 2017, the United States will have only a small contingent of troops, attached to the U.S. Embassy in Kabul.

The shortcomings of Afghanistan’s police take on new urgency in light of Iraqi security forces’ failure this summer to halt a major advance by the Islamic State militant group. The collapse of much of Iraq’s military, which was trained by the United States from 2003 to 2011, exposed the deterioration of Iraqi forces following the U.S. withdrawal.

SIGAR said that problems with management of Afghanistan’s police, which numbers about 153,000 people, included Afghan officials’ failure to properly use electronic and other systems for ensuring that salaries go to the right troops.

In one example, SIGAR said that Afghanistan’s police do not properly use identification cards issued to each recruit in part to track attendance. Potentially even more worrying, the report said officials do not confiscate the cards of troops who leave police service, meaning there are almost 150,000 invalid cards in circulation.

Inadequate tracking could heighten the police’s vulnerability to the kind of widespread corruption that has eroded many Afghans’ faith in government institutions over the past decade. While the country’s army has a positive reputation among many Afghans, the police are more problematic.

SIGAR also found that it is difficult for outside officials to cross-check data provided by the Afghan government. The watchdog faulted what it described as inadequate oversight by the United Nations and the U.S.-led NATO force in Afghanistan.

Since 2002, the United States has spent more than $15 billion to build Afghanistan’s national police force. Through a trust fund administered by the U.N. Development Program, the United States and other donor nations continue to fund police salaries and other costs. But without reliable data from the Afghan government, SIGAR said, donor nations cannot plan accurately and cannot know with reliability how many police officers are serving in which part of the country.

“As we go forward, it’s [the Afghans’] responsibility for doing the fighting, and basically the police are the ones that are out there,” said John Sopko, the special inspector general. “It’s important to know how many police there are.”

The United Nations’ management of the police trust fund has also come under fire from Afghan President Ashraf Ghani.

Maj. Gen. Todd Semonite, who heads the Combined Security Transition Command-Afghanistan, said in his response to the SIGAR findings that his goal is to implement a fully functional electronic accounting and personnel tracking system by January 2016.

He said his command will withhold U.S. military funding for the U.N.-administered trust fund until he is confident about the United Nations’ ability to oversee Afghan systems.

“In the past 90 days, we have applied significant pressure to enforce fiscal discipline and improve oversight,” Semonite said in a statement e-mailed to The Washington Post. “We will continue to enforce discipline in the system.”