A320 EXPERIENCES NMAC WITH B747-400 CLIMBING THROUGH ITS ALTITUDE BASED ON VISUAL SEPARATION.

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APPROX 10 NM E OF THE INTXN CAMRN ON A WESTERLY COURSE; ZNY ADVISED US OF OPPOSITE DIRECTION TFC IN OUR 11 O'CLOCK POS AT 8000 FT THAT WOULD BE CLBING TO 10000 FT. WE WERE LEVEL AT OUR ASSIGNED ALT OF 9000 FT. I ADVISED WE HAD A LIGHT IN SIGHT AT 11 O'CLOCK POS. THE B747-400 WAS CLRED TO CLB VISUALLY TO 10000 FT AND TO MAINTAIN VISUAL SEPARATION FROM US. WE COULD SEE THE PITCH CHANGE AS THE ACR Y STARTED ITS CLB. AT 6 MI SEPARATION; THE ACFT WAS 1500 FT BELOW AND CLBING. ZNY ISSUED A TFC POS CALL TO ACR Y; DESCRIBING OUR RELATIVE POS AND CONVERGING. ACR Y RPTED HE DID NOT HAVE US IN SIGHT. NEW YORK TOLD ACR Y THAT IF THEY DID NOT HAVE US IN SIGHT THEY MUST RETURN TO 8000 FT. I WAS NOT ABLE TO PAY ATTN TO THE REPLY FROM ACR Y AS OUR TCAS ISSUED AN RA (NO TA FIRST) WITH AN INSTRUCTION TO CLB AT A MINIMUM RATE OF 1300 FPM. THE TCAS INSTRUCTIONS WERE FOLLOWED. THE B747-400 PASSED 300-500 FT DIRECTLY BELOW US AS WE CLBED TO 9300 FT. WHEN COM PAUSED BTWN ACR Y AND ZNY; THE ACFT HAD ALREADY PASSED BELOW US AND I RPTED A TCAS CLB AT AN ALT OF 9300 FT NOW DSNDING TO 9000 FT. CTR TOLD US WE COULD TURN R IF WE NEEDED TO; BUT THE EVENT HAD ENDED BY THEN.