He doesn’t mean he could end it at any time. He says “if I’m elected” cause he’s talking about the time period after he won the election but before he actually took office.

The moment you win the election and become the person who will DEFINITELY be the president in a couple of months, your bargaining power with other nations (and anyone really) goes through the roof compared to what you had as a mere candidate.

I’ve stated that last as a fact though it’s just what seems self-evidently true to me.