WASHINGTON (Reuters) - The killing of three U.S. troops and wounding of dozens more on Sunday by Iran-backed militants is piling political pressure on President Joe Biden to deal a blow directly against Iran, a move he’s been reluctant to do out of fear of igniting a broader war.

Biden’s response options could range anywhere from targeting Iranian forces outside to even inside Iran, or opting for a more cautious retaliatory attack solely against the Iran-backed militants responsible, experts say.

American forces in the Middle East have been attacked more than 150 times by Iran-backed forces in Iraq, Syria, Jordan and off the coast of Yemen since the Israel-Hamas war erupted in October.

But until Sunday’s attack on a remote outpost known as Tower 22 near Jordan’s northeastern border with Syria, the strikes had not killed U.S. troops nor wounded so many. That allowed Biden the political space to mete out U.S. retaliation, inflicting costs on Iran-backed forces without risking a direct war with Tehran.