U.S. fighter jets launched airstrikes early Friday on two locations in eastern Syria linked to Iran’s Revolutionary Guard Corps, the Pentagon said, in retaliation for a slew of drone and missile attacks against U.S. bases and personnel in the region that began early last week.

The U.S. strikes reflect the Biden administration’s determination to maintain a delicate balance. The U.S. wants to hit Iranian-backed groups suspected of targeting the U.S. as strongly as possible to deter future aggression, possibly fueled by Israel’s war against Hamas, while also working to avoid inflaming the region and provoking a wider conflict.

According to a senior U.S. military official, the precision strikes were carried out near Boukamal by two F-16 fighter jets, and they struck weapons and ammunition storage areas that were connected to the IRGC. The official said there had been Iranian-aligned militia and IRGC personnel on the base and no civilians, but the U.S. does not have any information yet on casualties or an assessment of damage. The official would not say how many munitions were launched by the F-16s.

A senior defense official said the sites were chosen because the IRGC stores the types of munitions there that were used in the strikes against U.S. bases and troops. The two officials briefed reporters after the strikes on condition of anonymity to provide details on the mission that had not yet been made public.