Does encouraging my partner to apply for a job mean I've agreed to move?

My partner got the job he'd hoped for in another city. I hugged him, and he said, "We should start looking at places this weekend." I replied that I hadn't decided whether I'd move. His excitement disappeared.

When he applied, I had told him to go for it. The role sounded like something he'd enjoy. We had said we would talk about the rest if he received an offer. I thought that included whether I would relocate; he thought it meant discussing how we would do it.

I have a job, friends and a weekly class here that I don't want to leave without thinking. I am not opposed to moving. I am upset that my encouragement has turned into a commitment I didn't know I was making. He says he wouldn't have applied if he thought I might stay.

How do we return to a genuine decision without making my hesitation sound like withdrawing support for something I encouraged him to pursue?