AN ACR B767 IN FOREIGN AIRSPACE AND DEVIATING FOR WX HAS LOSS OF SEPARATION WITH ANOTHER ACR AT THE SAME ALT. BOTH ACFT WERE IN RADAR CONTACT.

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AT FL310 WE WERE DEVIATING AROUND TSTMS AROUND MANAUS. WE WERE IN RADAR CONTACT. WE HAD REQUESTED FL390. ABOUT 100 MI N OF MAN WE REINTERCEPTED UA300. ON TCASII ANOTHER ACFT POPPED UP 10 NM AHEAD ALSO AT FL310. WE ASKED MAN CTR ABOUT THIS BUT RECEIVED NO RESPONSE AND AGAIN REQUESTED FL390. AT 5 NM SEPARATION; I AGAIN REQUESTED TO KNOW WHO WAS AHEAD AT FL310. AT 3 NM I ADVISED MAN CTR THAT THERE WAS AN ACFT 3 NM AHEAD AT FL310 AND THAT WE WERE CLBING TO FL320. THE CTLR THEN GAVE US A CLB TO FL390. HE ASKED US IF WE WERE ON UA315. I TOLD HIM THAT WE WERE ON UA300 WHICH WAS OUR FILED RTE. I FINALLY GOT OUT OF THE CTLR THAT ACFT HAD BEEN ACR Y MANAUS TO BOA VISTA. AT THAT; I BEGAN WONDERING IF OUR HAND WRITTEN ATC FILED FLT PLAN HAD BEEN UP UA315 UNLIKE OUR COMPUTER FLT PLAN; WHICH WAS UP UA300. LATER; IT WAS FOUND THAT WE WERE ON THE CORRECT AIRWAY WITH BOTH THE ATC FILED AND THE COMPUTER FLT PLAN WERE UP UA300. THE CTLR ASKED IF WE HAD BEEN CLRED DIRECT PAKON. I REALLY DON'T KNOW. IF WE WERE I MISSED IT. EVEN IF WE WERE AFTER THE DEV WE WOULDN'T HAVE BEEN MUCH OFF THE AIRWAY. IF WE DID MISS THE CLRNC WHY? LANGUAGE -- CLOSE FLT NUMBERS WITH ANOTHER ACR? SWITCHING BREAKS? WHY DIDN'T THE CTLR CATCH IT IF WE WERE IN RADAR CONTACT? THANK YOU TCASII.