publications - Mentor trying to be first author?

I was on an internship with professor A at University B in China. We were working on a computer science project. During the internship I implemented professor A's idea and got some results. Three weeks ago I finished a paper draft and left University B for a new internship. Me and professor A were planning to submit the paper draft to a conference (deadline: May 20).

Until yesterday (May 17), the order of authors was: me, professor A, other students & collaborators in the lab... And professor A had no objection with that. However, last night I received an email from him. He said he wants to be the first author... His reason was for intellectual properties and patent issues. My understanding is that because I was merely an intern at University B, if the first author was me, it would cause IP troubles for him?

I feel deceived. But, should I feel like this? I was counting on a first-author paper because I'm planning to apply for a PhD program in the US. One paper may not mean a lot to someone who's published a lot. But for someone who hasn't published yet, it means something.

Looking on the Internet, I found something that might explain professor A's motivations: In China specifically, corresponding authors are often underappreciated by universities and research institues. This might be the case for University B. Given professor A is relatively young, he may want first authorship for promotion.

Summary of my questions:

1. Should I go discuss with professor A and try to persuade him to let me be the first author?



2. If I want to apply for a PhD program in the US, would being the first author be more helpful or being the second author is as well helpful?

Edit:

1. My affiliation for the paper has always been University B. I didn't mention my current university or internship in any sense.


2. I emailed back to professor A yesterday, saying I think I should be the first author, because I did most of the work; because the idea was originated from him he should be the corresponding author. He replied this morning, saying he agree with what I said. He explained that because I was doing an internship in his lab and not a student of University B, putting me as the first author could cause IP and patent troubles for University B... So this problem is fixed now.