He's not sure he understands the words, the concept, well enough to be comfortable saying them. Not just yet. Is he attracted to her? No question of that. Does he want to be with her? Little doubt. Can he make a commitment, that such a statement implies, right now?
He's not sure. He needs to understand it better, to know what it is he feels, before he can do that.
"I'll get those forms finished," he replies, tucking the ring into his shirt pocket.