The U.S. military airdropped 50 tons of small arms ammo and grenades in northern Syria on Sunday, a senior defense official told Fox News, representing the Pentagon's shift from training rebel fighters to equipping them. 

Coming just two days after the Defense Department announced it was effectively ending its current training program, the airdrop delivery was made Sunday by four C-17 transport aircraft. The 112 pallets contained ammunition for M-16s and AK-47s. 

"All the pallets reached friendly forces," the official said, adding that the drop "looked similar to what we did in Kobani." This referred to one of the few bright spots in the war against the Islamic State when the U.S. military dropped weapons to Syrian Kurdish fighters, known as the YPG, who successfully expelled ISIS from the Turkish-Syrian border town of Kobani earlier this year. 

This time, the official said Syrian Kurds were not recipients of the U.S. airdrop -- only Syrian Arabs fighting ISIS. There is sensitivity in Washington over arming Syrian Kurds, whom Turkey sees as an enemy but the U.S. counts as a NATO ally. 

The 50 tons of supplies were airdropped into Al-Hasakah province, home to Syrian Kurds, Arabs and a minority Assyrian community. 

More On This...

The ammunition originally was intended for the U.S. military's "train and equip" mission, the official said. But that program was canceled last week. 

"So now we are more focused on the 'E' [equip] part of the T&E [train & equip]," said the official, who described equipping Syrian Arabs as the focus of the new strategy against ISIS. 

The Defense Department announced Friday that it was overhauling the mission to aid Syrian rebel fighters. After the program fell far short of its goals for recruiting and training Syrian fighters, the DOD said it would focus instead on providing "equipment packages and weapons to a select group of vetted leaders and their units so that over time they can make a concerted push into territory still controlled by ISIL." 

The shift also comes as Russia continues to launch airstrikes in Syria, causing tension with the U.S. amid suspicions Moscow is only trying to prop up Bashar Assad. 

Col. Steve Warren, spokesman for the U.S.-led anti-ISIS coalition, confirmed that coalition forces conducted the airdrop on Sunday. 

"The aircraft delivery includes small arms ammunition to resupply counter-ISIL ground forces so that they can continue operations against ISIL. All aircraft exited the drop area safely," he said in a statement. 

President Obama, in an interview on CBS' "60 Minutes" aired Sunday, said there's "no doubt" that the training mission "did not work." But he noted he was "skeptical from the get-go about the notion that we were going to effectively create this proxy army inside of Syria." 

Obama said while there are no "silver bullets," the U.S. is "prepared to work both diplomatically and where we can to support moderate opposition that can help convince the Russians and Iranians to put pressure on Assad for a transition."

Lucas Tomlinson is the Pentagon and State Department producer for Fox News Channel. You can follow him on Twitter: @LucasFoxNews