A319 LNDG LAX ON THE RWY COMPLEX RPTED NMAC WITH PARALLEL RWY TFC AT APPROX 2500 FT.

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WE WERE CLRED FOR ILS RWY 25L APCH AFTER FUELR. ADVISED BY APCH TO EXPECT SWITCH TO ILS RWY 25R. ATC ASKED IF WE HAD THE RWY PRECEDING TFC IN SIGHT. WE TOLD THEM WE HAD NEITHER. WE HAD AN INFLT VISIBILITY OF APPROX 2-3 MI IN HAZE. ATC ADVISED US OF A 'BRASILIA' FROM OUR L WHO WOULD BE LNDG ON THE L AND WE WOULD BE FOR THE R. ATC ASKED AGAIN IF WE HAD THE PRECEDING B737 IN SIGHT. WE AGAIN SAID 'NO.' ATC SAID HE WOULD HAVE TO LEVEL US AT 3000 FT IF WE DIDN'T GET THE RWY OR PRECEDING TFC IN SIGHT. THE PNF THEN ACQUIRED THE TFC AND TOLD ATC. HE THEN CLRED US FOR ILS RWY 25L APCH. THE PNF LOADED THE APCH AND WE MADE A TURN TO INTERCEPT. ALMOST SIMULTANEOUSLY WE GOT AN TCAS TA 'TFC; TFC' ALERT FOLLOWED IMMEDIATELY BY AN RA; 'CLB; CLB.' THEN 'INCREASE CLB.' I IMMEDIATELY DISCONNECT THE AUTOPLT AND FOLLOWED RA GUIDANCE AND LEVELED OFF AT APPROX 4000 FT. THE PNF INFORMED ATC THAT WE HAD DONE A TCAS CLB AND GOT INSTRUCTIONS TO DSND TO 3000 FT. WE WERE THEN VECTORED FOR ANOTHER APCH AND LNDG WHERE WE BROKE OUT ABOUT 700 FT AGL AND 2.5 MI. I CALLED THE LAX TWR AND INFORMED THEM I WANTED THEM TO START THE PROCESS FOR AN NMAC AS WE SHOWED THAT AN ACFT HAD MERGED WITH US ON OUR NAV DISPLAY AND INDICATED 100 FT BELOW US.