India, July 30 -- The stop-start conflict between the United States and Iran entered a new phase as Saudi Arabia joined the U.S. in striking Iran-backed militias in Iraq, while diplomatic efforts to end the fighting stalled amid deepening mistrust between the longtime adversaries.

The renewed military action came after several days of relative calm and raised fears that the conflict could again spiral into a wider regional war. Iran said it launched ballistic missiles at a key U.S. military base in Jordan, while U.S. and Saudi forces struck logistics and weapons sites used by Iran-backed militias in Iraq.

The developments have further complicated efforts to revive diplomacy, with no clear path toward negotiations. Iran's deputy foreign ...