ATC WAS EXPECTING THE FLC OF AN MLG TO START CLBING AT ONCE WHEN INSTRUCTED TO MAKE A MISSED APCH.

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ON APCH TO SFO RWY 28R WE WERE TOLD TO SLOW TO 180 KTS THEN 160 KTS. WE WERE CLRED FOR THE ILS RWY 28R APCH. WHEN WE SWITCHED FREQ TO SFO TWR WE WERE TOLD TO SLOW TO FINAL APCH SPD WHICH WAS 145 KTS. THE PRECEDING B767 ACFT HAD SLOWED TO 120 KTS. THE TWR TOLD US THAT 'THIS ISN'T GOING TO WORK; GAR; FLY THE PUBLISHED MISSED.' WE LEVELED OFF AT 1650 FT AND PROCEEDED TO FLY TO THE PUBLISHED MISSED APCH POINT; LEVEL AT 1650 FT MSL. THE PUBLISHED MISSED APCH ALT IS 3000 FT AND THE PROC STARTS AT APPROX THE MIDDLE MARKER. I UNDERSTAND THE AIM TO STATE THAT WE SHOULD FLY TO THE MISSED APCH POINT AT OR ABOVE MDA OR DECISION HT AND THEN START THE MISSED APCH PROC. BY LEVELING AT 1650 FT WE WERE AT OR ABOVE DECISION HT OR MDA. SFO TWR THOUGHT WE WOULD START TO CLB IMMEDIATELY BUT DID NOT REQUEST US TO DO SO. BECAUSE WE WERE NOT INSTRUCTED TO CLB AND WE LEVELED AT 1650 FT MSL; WE LOST TFC SEPARATION WITH THE PRECEDING ACFT. TWR WANTED US TO CLB AND ASKED IF WE WERE GOING TO. WHEN WE TOLD HIM THAT WE WERE LEVELING OFF TO THE MISSED APCH; HE TOLD US TO CLB AND MAINTAIN 3000 FT. WE LATER LEARNED THAT WE LOST SEPARATION WITH THE PRECEDING ACFT. TO PREVENT THIS FROM HAPPENING AGAIN I SUGGEST THAT THE TWR CTLR TELL US WHAT THEY REALLY WANT US TO DO. IF WE ARE CLRED TO CLB PRIOR TO REACHING THE MISSED APCH; IT SHOULD BE STATED IN THE AIM.