My understanding, and this was from comments that one of the Deputy Secretaries or Commanders of the US Navy said, was that at Jakarta, in a presentation made by a high ranking PRC official, it was announced that the PLAN would be attending RIMPAC 2014 and was accepting the US invitiation. Excatly how that occurred in terms of who passed it along, at least to me, is immaterial.
As it stands, the US is moving forward with China coming and has announced openly as much, and the PRC has certainly not announced that this is a mistake. We do not know otherwise, outside of these announcements, what is happening back channels.
My read from this line:
Deputy Defense Secretary Ashton Carter acknowledged China had agreed to participate in RIMPAC during a little-noticed speech on Wednesday in Jakarta.
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Deputy Defense Secretary Ashton Carter acknowledged, China had agreed to participate in RIMPAC, during a little-noticed speech on Wednesday in Jakarta.
Carter was the one that made the speech