A U.S. Marine guides a howitzer to a firing position May 14 in Syria. (Sgt. Matthew Callahan/Marine Corps)

Defense Department officials were pressed Monday to explain inconsistencies between their official statements about troop counts in multiple war zones and statistics made publicly available on government-operated websites, discrepancies that raise questions about the deployment of U.S. forces worldwide.

Defense Secretary Jim Mattis has made assurances that his agency would be more forthcoming about how many troops he has committed to operations in Syria, Iraq, Afghanistan and elsewhere, but those changes have not taken effect.

A Pentagon spokesman, Army Col. Rob Manning, said Monday there were about 500 U.S. troops in Syria, a number far short of the 1,720 listed in the most recent quarterly report furnished by the Pentagon’s Defense Manpower Data Center. In Iraq, the number is 8,892 troops — substantially higher than the 5,000 Manning said are there.

The data center’s latest worldwide deployment data, accurate as of Sept. 30, was released on its website Nov. 17.

Speaking to the Pentagon press corps, Manning offered some explanations as to why the numbers can be different.

They can fluctuate, he said, as troops rotate in and out of a region. Sometimes, he added, political sensitivities and agreements may limit the public disclosure of troop levels in certain countries. Security concerns also make it risky to tabulate precisely how many troops are stationed in any given place, he said.

The Defense Department data does not include such disclaimers.

The issue has taken on new significance since four American soldiers were killed Oct. 4 in Niger, which hosts a U.S. drone base and relies on U.S. Special Forces for training and guidance in its struggle with Islamist militants.

A year ago, the Defense Department’s public data disclosed the presence of just seven troops in Niger, a number that remained largely unchanged until this month, when the latest data report jumped to 536. Earlier this year, in a disclosure to Congress, the White House indicated there were 645 American troops in the country. Immediately after the deadly ambush, military officials said there were 800 troops in Niger.

The Defense Department’s publicly disclosed data, which tracks U.S. personnel levels in dozens of countries, are “not meant to represent an accurate accounting of troops deployed to any particular region,” said Eric Pahon, a Pentagon spokesman. That may change soon, Pahon said, as the Pentagon takes a “hard look” at the utility and value of the manpower data it provides in its quarterly reports.

The 500 figure officials cite as the U.S. troop presence in Syria is the “force management level,” a cap set by President Barack Obama’s administration to limit the U.S. personnel there and in Iraq, where operations against the Islamic State have been conducted primarily by local forces supported by U.S. firepower and advice.

Obama was reluctant to deepen the U.S. commitment there, said Todd Harrison, a defense analyst at the Center for Strategic and International Studies, a Washington think tank. The preference for a small U.S. military footprint — limited early on to Special Operations troops, attack helicopters and artillery units — led to loose definitions and fuzzy accounting, he said.

“They didn’t count all boots on the ground,” he said, adding that officials in the Trump administration are still grappling with earlier practices that do not give a clear picture of where U.S. troops are deployed.

“It’s given the public and Congress a false sense over how overstretched the military really is,” he said.