U.S. military cargo planes on Sunday airdropped 50 tons of small arms ammunition and grenades to Syrian Arab rebels in northern Syria, marking the beginning of the Pentagon's shift away from its failed program to train rebels and toward its new strategy of arming existing groups instead.

Four C-17 transport aircraft dropped 112 pallets containing ammunition for M-16s and AK-47s into Al-Hasakah province, according to Fox News.

"Coalition forces conducted an airdrop Sunday in northern Syria to resupply local counter-ISIL ground forces as they conduct operations against ISIL," said Col. Steve Warren, the spokesman for Operation Inherent Resolve in Iraq, using the acronym preferred by the U.S. government for the Islamic State group or ISIS, reports ABC News. "This successful airdrop provided ammunition to Syrian Arab groups whose leaders were appropriately vetted by the United States and have been fighting to remove ISIL from northern Syria. Due to operational security we will not have any further details about the groups that received these supplies, their location, or the type of equipment in the airdrop," Warren added.

Last week, the Obama administration shelved a $500 million program to train and equip so-called moderate rebels opposed to Syrian President Bashar al-Assad who would be directed to fight against ISIS. The program had sought to train some 5,400 rebels but in the end only managed to produce a handful of combat-ready fighters.

The Pentagon's program to train and arm rebels fighting ISIS is separate from the ongoing CIA program to train rebel fighters working to overthrow Assad.

Two weeks ago, Russia intervened in the war on behalf of Assad and is reportedly conducting coordinated attacks with Syrian government forces against both ISIS and the U.S.-backed anti-government rebels.

The U.S. has reprimanded Moscow for its decision to prop up Assad and said it will not be cooperating militarily with the country, while Moscow insists the U.S. is making a mistake by arming the rebels and intensified airstrikes on Monday in central Syria.

The European Union on Monday called on Russia to stop its military intervention, claiming that it could prolong the four-year-long war and undermine the political process, reports the Guardian.

Russian President Vladimir Putin said Sunday that Russia is "working in strict compliance with the international law, at the request of the Syrian authorities," according to Press TV.

The U.S. has been conducting airstrikes against ISIS since September of 2014, spending billions of dollars doing so and killing a reported 10,000 extremist fighters. Yet despite this effort, as of July ISIS was fundamentally no weaker than it was when the U.S. campaign began a year ago, according to The Associated Press.

Putin said that he cannot understand how the U.S. military can claim it is fighting terrorism but not produce any "real results." Syria's Ambassador to Russia Riad Haddad told Sputnik News last week that 40 percent of ISIS' infrastructure has been taken out since Russia entered the conflict two weeks ago.