Your dog is on a lead, which is the correct decision at this age. A loose dog is 60 feet away and coming, and their owner is somewhere behind, calling.
Your dog is now pulling, barking or spinning on the end of the lead. You are the only one in this picture with a plan.
Why this is so much harder than a normal walk
Your dog can see a dog they want to reach and cannot reach it. The lead is doing its job, and it is also the source of the frustration.
Reduced responsiveness to the cues of the person who raised them appears around the onset of adolescence, and returns later in the stage. That is exactly why your dog is on a lead in the first place.
A dog this close to something this interesting is over the threshold at which they can learn. Working below that threshold is the condition for learning near a trigger, so nothing you teach in these 10 seconds will stick.
In the moment: get moving, get distance
Turn and walk away at once, before the gap closes. Distance is the only tool that works this quickly, and it costs you nothing.
Keep your dog moving with you rather than standing still to face the other dog. A dog on the move is easier to hold and less likely to fixate.
Feed as you walk, from your hand, at your leg. Not as a reward for anything in particular, but to give your dog something to do that is not staring.
Get something solid between the dogs where you can: a parked car, a bench, a tree, a gate, the corner of a building.
Shorten the lead by taking it in your hand, and keep it as loose as you can. Hauling backwards adds to the tension your dog is already feeling.
Your body matters here. Stand side-on rather than square, keep your shoulders turned away from the incoming dog, and stay off your dog's back and collar.
Talking to the other owner
Call out early, loudly and clearly, while you still have 40 feet. Say the one sentence that works: my dog needs space, please call your dog.
Say it as information rather than an accusation. You need that person to act in the next 5 seconds, not to feel judged.
If the dog arrives anyway, keep walking away and keep talking calmly. Do not grab, kick at or shout at the other dog.
If a greeting happens and both dogs are loose and wiggly, let it be short, then move off. A 3 second hello ends better than a 30 second one.
You are allowed to say no to a greeting. An owner who tells you their dog is friendly has told you about their dog, not about yours.
What to train for this, starting this week
The skill is not recall from 100 feet. It is a turn away from a dog your dog has noticed, which is a much smaller thing to build.
Teach an emergency turn on a quiet street. Say your word, turn, walk 10 feet, feed 3 times. Run 5 reps a day with no other dog present.
Add a distant dog next. Stand far enough out that your dog can look and then take food, and do 1 turn away for each look.
Practise your check-in at that same distance. Pay every time your dog looks at the dog and then back at you, with no cue at all.
Only close the distance when your dog is eating easily. A dog who will not take food is telling you to move further out.
Behaviour change is built from management plus reinforcement. The management half is the walk you choose, and it does more work than the training half this month.
Choose your ground while this is unreliable
Walk where loose dogs are least likely: early mornings, pavements, quiet lanes, or a securely fenced field you can book.
Carry the lead on a well-fitted harness rather than a collar, and use a 6 foot lead rather than an extending one for this.
Learn the 2 or 3 spots on your route where a loose dog usually appears, and have your exit picked before you get there.
Reward-based methods are what is recommended for training and behaviour change, and survey work associates them with higher reported responsiveness. Nothing about a difficult encounter changes that.
Safety note
Get help now if your dog has bitten another dog, been bitten, or is lunging and snapping at every dog they see. That needs a veterinary examination and a qualified behaviour professional who can watch your dog in person. Sudden change in how your dog reacts to other dogs warrants a veterinary check too. Pain frequently presents as a change in behaviour rather than as obvious lameness.
Today's version, in one line: 5 emergency turns on a quiet street, and one sentence rehearsed out loud for the next loose dog.