我正在办。take a long time. I found an agent to do that for me

First, I wrote a letter (in both languages) and get Notarized in local office (such as your bank), then sent that to my agent. Then he submitted that to state to get authorization (in my case, took about a week), then submitted it to US DOS on Sep 7, so far, haven't get it back yet. My agent told me might need another 10 days (estimated). When get back, submit those files to 中国大使馆 which might take another 10 days.