B737 FLT CREW WITH ZLA AT FL250 DESCRIBED CONFLICT WITH OPPOSITE DIRECTION TFC AND RESPONDED TO TCAS RA PREVENTING A LOSS OF LEGAL SEPARATION.

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DURING STEP CLB TO FL340; WE WERE VECTORED SLIGHTLY OFF THE GORMAN DEP AND THEN GIVEN ON COURSE TO GMN BY ZLA. WE WERE ASSIGNED FL250; LEVELED OFF; AND WERE TOLD OF TFC AT 10 O'CLOCK POS AT FL250 AND 8 MI. WHILE SEARCHING FOR THE TFC ON A 310 DEG HDG; WE RECEIVED A TCAS TA QUICKLY FOLLOWED BY AN RA. I WAS THE PF (FO); SO I IMMEDIATELY DISENGAGED THE AUTOPLT AND FOLLOWED THE TCAS GUIDANCE TO CLB WHILE LOOKING AHEAD FOR THE INTRUDER TFC NOW AT 12 O'CLOCK POS. THE CAPT AND I INITIALLY PICKED UP THE TFC VISUALLY APPROX 3 MI AWAY AND CROSSED OVER THE TOP OF THE OTHER CARRIER RJ BY APPROX 1000 FT. THE TFC WAS HDG APPROX 090-100 DEGS AT FL250. DURING THE AVOIDANCE CLB; I BELIEVE THE CTLR DISCOVERED THE CONFLICT AND BEGAN TO REISSUE ALT ASSIGNMENTS; BUT BECAUSE OF THE TCAS RA AUDIO TO 'ADJUST VERT SPD' AND 2 JUMPSEATERS TELLING ME TO CLB AND POINTING OUT THE TFC; I COULDN'T UNDERSTAND THE CTLR'S CALL. AT THIS POINT THOUGH; HIS INSTRUCTION WAS MEANINGLESS AS THE ACFT WERE ABOUT TO MERGE. I BELIEVE THE CTLR ERRED IN ASSIGNING BOTH ACFT THE SAME ALT; ALTHOUGH I'M NOT SURE WHY THIS OCCURRED (DISTR; LOSS OF SITUATIONAL AWARENESS...). FURTHER REVIEW OF THE ATC TAPES SHOWED 5 MI OF LATERAL SEPARATION WHILE BOTH ACFT WERE AT FL250; AND 1100 FT OF VERT SEPARATION AT THE MERGE POINT.