CLRED FOR A VISUAL APCH TO FOLLOW A B757 AN AIRBUS SLOWS WHEN UNABLE TO MAINTAIN SPACING AS THE PRECEDING B757 BEGAN TO SLOW. ATC IS NOTIFIED OF A SPD REDUCTION BELOW ASSIGNED AND LONG LNDG WAS REQUESTED. A THIRD (FOLLOWING) ACFT WAS DIRECTED TO GO AROUND BY ATC.

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LONG FINAL ON RWY 12; SLOWED TO FOLLOW B757 FOR SAME RWY. INITIALLY 5 MI IN TRAIL ON A VFR DAY. APCH ASKED IF WE HAD THE B757 IN SIGHT; WE SAID WE DID. CLRED VISUAL BEHIND THE B757; SPD 190 KTS TO THE MARKER. NORMALLY THAT WOULD NOT BE TOO MUCH OF A PROB. CONTACTED THE TWR AND NOW REALIZED THE B757 WAS SLOWING. TWR CLRED US TO LAND AND TURN OFF AT TXWY Q4. WITH CALM WINDS; AND NOW BARELY 3 MI BEHIND THE B757; WE ADVISED ATC THAT WE WOULD BE SLOWING BELOW THE ASSIGNED SPD IN ORDER TO MAINTAIN ADEQUATE SEPARATION. ADDITIONALLY WE ADVISED THEM; THAT DUE TO THE PROX OF THE B757; AND THE CONCERN ABOUT HIS WAKE TURB; WE WOULD BE UNABLE TO TURN OFF AT TXWY Q4 BECAUSE WE WOULD BE LNDG ABOVE THE B757 WAKE. TWR UNDERSTOOD AND APPROVED TXWY Z TURNOFF IF NEEDED. IN THE FLARE WE DID ENCOUNTER SOME WAKE TURB; BUT IT WOULD HAVE BEEN WORSE IF LNDG HAD BEEN MORE ON GS. DUE TO OUR NEED TO TURN OFF AT TXWY Z; THE TWR TOLD THE NEXT AIRPLANE TO GO AROUND. WE WERE BEING SQUEEZED BY ATC TO KEEP THE SPD HIGH; CLOSE IN TO AN AIRPLANE WITH WAKE TURB CONCERNS; AND TO TRY TO MAKE A TURNOFF AT ATC'S REQUEST. WE FELT THE PRUDENT THING TO DO WAS FLY ABOVE THE WAKE AND TAKE A LATER TURNOFF.