A B767 RPTED AN NMAC WITH AN MD11 OR DC10 WHILE ON THE PARADISE 3 ARR FOR LAX.

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ARRIVING VIA THE PARADISE 3 TO RWY 25L. PASSED TEJAY NORMALLY; SLOWING TO 250 KTS AND DSNDING VNAV PROFILE. APCHING MITTS INTXN AND ABOUT 11000 FT; WE WERE ADVISED OF AN ACFT TO OUR R WHO HAD US VISUALLY AND WOULD MAINTAIN SEPARATION. I 'ROGERED' THE CALLOUT AS IT WAS DARK AND WE DID NOT WANT TO MAINTAIN VISUAL SEPARATION. I TOLD THE CAPT I SAW THE ACFT AND IT WAS NOT MOVING ON MY WINDSCREEN; INDICATING A CONVERGING VECTOR. AS WE DSNDED INTO THE BLOCK ALT FOR MITTS; WE RECEIVED A TCASII RA TO DSND. WE BEGAN THE PROC AND TOLD ATC AND KEPT VISUAL ON THE ACFT. NO SOONER THAN WE GOT WORD TO ATC DID TCASII REVERSE COMMAND TO A CLB. BY THEN THE ACFT WAS SO CLOSE I COULD TELL IT WAS AN MD11 OR DC10 AND APPEARED TO HAVE CARGO MARKINGS. THE ACFT PASSED DIRECTLY OVER US AND INTERCEPTED THE RWY 25L FINAL. WE WERE AT 9000 FT BY THIS TIME AND CLRLY BELOW OUR ALT RESTRS. THIS VISUAL ACFT SHOULD HAVE MANEUVERED TO STAY WELL CLR. ATC SHOULD HAVE TAKEN THE OTHER ACFT TO RWY 24R AND LEFT US ON RWY 25L; THUS NOT NEEDING THE XING CONFLICT. ATC WAS NO HELP. WE SHOULD HAVE DECLARED A NEAR MISS AND HAD THE TAPES MARKED. BY THE TIME WE WERE CLR OF CONFLICT WE WERE SO SPEECHLESS AND DISTURBED WE COULDN'T SAY ANYTHING. SUPPLEMENTAL INFO FROM ACN 461384: CLRED FOR THE PDZ.PDZ3 TO RWY 25L. SUBSEQUENTLY CHANGED TO PDZ3 TO RWY 24R TRANSITION.