As usual, Rudi's info is reliable. Look at United's website. They are joining Star Alliance in 1999 (United's Press Release). ANA's website also says:

"By around October 1999, ANA will become an official member of the Star Alliance. However, ANA will commence services such as joint frequent flyers' program, through check-in and common use of airport lounge with partner airlines when ready. Code share operation, joint marketing and advertisement will also be considered."