Peter dampens his lips. There's a part of him that doesn't want to give Liz false hope and a desperate part of him who wants to be mature about this, like nearly ever adult here who insists that it's impossible. (They were mature, right? Most of the time they treated him like he wasn't, so... if he acted like them, they'd think he was mature, wouldn't they?)

But in the end, he says what he wants to.

"If we can find a way..." He hesitates, but then pushes forward. "...you should come with me."