Dogs are social beings, just like us. When we want to engage with someone, we make eye contact, we turn in their direction, we may reach a hand out to touch an arm. When we walk on the street and see an approaching person we may look away or down to avoid an awkward moment of "do I or don't I make eye contact and smile".
We have that moment because we are social and have learned once we acknowledge the other person, we are socially obligated to address them in some manner.
How many times has your dog stood in front of you staring and staring and staring? Chances are you either give him what he is asking for, perhaps a belly rub or you have a one sided conversation giving the many reasons why now is not a good time.
Because dogs are social, that conversation is usually seen as an invitation to engage.
If you don’t want to interact with your dog at a particular time you should avoid the urge to have a long chat about why not ☺
As long as you are maintaining contact with your dog via chit chat or eye contact, he will continue to attempt to engage with you.
When I am sitting on the couch watching t.v. or reading and find a dog staring at me, I either get up and go to another room, turn my gaze away to avoid eye contact or cross my arms and look away.
Any of those gives a clear signal that I am not interested. Sometimes they will walk away immediately, sometimes it takes a few moments before they walk away.
Try it one day. Simply cross your arms, turn your head to the left or right, say nothing. Wait and see how long it takes your dog to walk away or lie down.