RPTED LOSS OF SEPARATION FROM APPARENT CONFUSION WHEN ACR X; WITH CLRNC TO FL390; MISINTERPS INSTRUCTIONS FROM THE RADIO OPERATOR AND DSNDS BACK TO FL370 AND CONFLICTS WITH ACR Z AT FL370. THE RADIO OPERATOR WAS ATTEMPTING TO CLB ACR Y; A COMPANY ACFT; TO ACR X WITH A SIMILAR CALL SIGN.

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ACR X WAS ENRTE FROM NEW ZEALAND TO KOREA ALONG ATS RTE G339. THIS RTE TAKES THE ACFT THROUGH AIRSPACE CTLED BY THE GUAM CERAP. DURING THE XFER COORD WITH THE GUAM CTLR; THE ZOA CTLR REQUESTED THAT A CLRNC BE ISSUED TO ACR X TO CROSS 20 DEGS N LATITUDE AT FL390. ACR X WAS AT FL370. THIS WAS ACCOMPLISHED AS REQUESTED. ACR X ATTEMPTED TO CONTACT HONOLULU RADIO TO RPT LEAVING FL370 AS REQUIRED BY ICAO RULES. AT THIS SAME TIME; THE HONOLULU RADIO OPERATOR WAS ATTEMPTING TO ISSUE A CLRNC TO ANOTHER ACFT; ACR Y; TO CLB TO FL370. WHEN THE OPERATOR HEARD ACR X ON FREQ; THE ERRONEOUS ASSUMPTION WAS MADE THAT THIS ACFT WAS TAKING THE CLRNC INTENDED FOR ACR Y. IN FACT; EACH XMISSION FROM ACR X INDICATED THAT THE ACFT WAS LEAVING FL370 TO CROSS 20 DEGS N AT FL390. THE RADIO OPERATOR ASSIGNED ACR X A NEW FREQ TO MONITOR; AND THEN ISSUED THE CLRNC FOR ACR Y AGAIN. WHEN ACR X AGAIN ATTEMPTED TO RPT LEAVING; THE RADIO OPERATOR STATED 'NEGATIVE; THAT CLRNC IS FOR ACR Y.' ACR X RPTED LEVEL AT FL370; WITH AN ESTIMATE FOR WAYPOINT PAKDO. THE ACFT HAD INITIATED A CLB TO FL390 AS PREVIOUSLY CLRED; BUT RETURNED TO FL370 BASED ON INFO RECEIVED FROM THE HONOLULU RADIO OPERATOR. THE ZOA CTLR CONTACTED TOKYO ACC AND ADVISED THEM THAT ACR X WAS AT FL370 AND THAT ATTEMPTS TO ISSUE A NEW CLRNC TO FL390 HAD BEEN UNSUCCESSFUL. TOKYO ACC HAD TFC; ACR Z; AT FL370; AND SEPARATION WAS LOST BTWN THAT ACFT AND ACR X. HONOLULU RADIO WAS EVENTUALLY ABLE TO ESTABLISH COMS WITH ACR X; AND THE ACFT WAS CLRED TO FL390. THIS WAS AN FAA OPERROR. FOREIGN LANGUAGE COMPREHENSION WAS A FACTOR IN THIS ERROR AS WELL AS THE RADIO OPERATOR NOT BEING AWARE OF A CLRNC HAVING BEEN DELIVERED THROUGH ANOTHER AGENCY (GUAM CERAP).