The United States said on Monday it carried out an ammunition airdrop for Syrian Arab groups battling Islamic State, as Washington shifts its focus to arming fighters inside Syria after ending a failed program to train a new rebel force.

US air force C-17 cargo aircraft flew into northern Syria on Sunday to carry out the mission and all aircraft exited the airdrop area safely, the US military’s Central Command said.

The US military did not name the individual groups that received the small arms ammunition but said their leaders had been screened by the United States, which wants to avoid weapons falling into the hands of Islamic State and al Qaida-linked fighters.

“This successful airdrop provided ammunition to Syrian Arab groups whose leaders were appropriately vetted by the United States,” spokesman Colonel Patrick Ryder said in a statement.

The airdrop came barely two weeks after Russia raised the stakes by intervening in the war on the side of President Bashar al-Assad and just days after Washington shelved a US military program to train and equip thousands of “moderate” rebels.

Barack Obama is seeking to retool his Syria strategy to build off some successes in northern Syria, where US-led airstrikes bolstered Kurdish forces battling Islamic State, including in the border town of Kobani.

A US military official, speaking to Reuters on condition of anonymity, said the US airdrops were part of the new approach.

Reuters has reported that part of the proposed new US campaign envisioned providing US support to the Syrian Arab Coalition, which would operate east of the Euphrates river. It would push south toward Raqqa.

The proposed US strategy would also bolster a group of mostly Arab fighters west of the Euphrates to clear out Islamic State along a pocket of terrain along the border with Turkey.

The U.S. military, however, declined to provide further details about the groups that received the supplies, their location, or the type of equipment in the airdrop.

“This airdrop seeks to build on the success those forces have had clearing Isil from Syrian territory,” Ryder said, using an acronym for Islamic State.