Washington has blamed the spike in violence on Tehran-backed forces and carried out strikes on sites in Syria it said were linked to Iran on three separate occasions, but the drone and rocket attacks have continued.

"Since October 17 through today, we are tracking that there have been 55 attacks on US forces. There have been 27 attacks against US forces in Iraq and 28 attacks in Syria," Deputy Pentagon Press Secretary Sabrina Singh told journalists, putting the number of injured American personnel at 59.

The surge in attacks on US troops is linked to the war between Israel and Hamas, which began when the Palestinian militant group carried out a shock cross-border attack from Gaza on October 7 that Israeli officials say killed about 1,200 people.

Following the attack, the United States rushed military aid to Israel, which has carried out a relentless air, land and naval assault on Hamas-controlled Gaza that the territory's health ministry says has killed more than 11,300 people.

Those deaths have sparked widespread anger in the Middle East and provided an impetus for attacks on American troops by forces opposed to their presence in the region.

There are roughly 2,500 American troops in Iraq and some 900 in Syria as part of efforts to prevent a resurgence of the Islamic State group.

The jihadists once held significant territory in both countries but were pushed back by local ground forces supported by international air strikes in a bloody, multi-year conflict.