Your dog sees another dog and goes still. Their body tightens, the lead shortens, and a few seconds later they bark or lunge. That pause is useful information. It may be an early sign that the situation is becoming too much. Do not stand still waiting to see if they will behave this time.
Create space calmly. Cross the street if it is safe, turn down another path, or put a visual barrier between the dogs. Use a secure, well-fitting harness and lead you can handle. Do not allow an on-lead greeting to "work it out," especially if either dog cannot move away. If your dog has bitten, is hard to control, or the route has no safe escape, seek help from a qualified, reward-based behavior professional.
Work before the stare
On a quieter route, notice how far away another dog can be while yours remains loose enough to sniff, eat, and turn toward you. Reward seeing the dog at that easier distance, then move away. Rehearse a cheerful U-turn without triggers so you can use it when one appears unexpectedly. If your dog locks on, you are already too close for teaching, focus on leaving safely.
A dog may stare because of fear, frustration, or high arousal. The plan does not require you to diagnose that in the moment. Distance gives you room to observe, and a professional can help tailor the work if reactions persist. A sudden change in behavior also deserves a veterinary check.
The win is not squeezing past another dog without a sound. It is noticing the first sign and helping your dog stay under their limit. For a longer plan on noticing other dogs without a lunge, see the leash-reactivity guide, that early freeze is your cue to make space
Sources: Dogs Trust: Reactive dogs - why it happens and how to help. Dogs Trust: How to understand your dog's body language.