THE FLC OF AN ACR B737 HAD A LIGHT TWIN CLRED FOR TKOF ON THEIR RWY WHEN THEY WERE ABOUT 1000 FT AGL.

Narrative

WHILE WE WERE FLYING THE ILS RWY 10 AT ABOUT 1000 FT TO SJU; THE TWR CTLR CLRED A LIGHT TWIN FOR TKOF ON RWY 10. I DID NOT SEE ANY TFC AT FIRST AS I SCANNED THE END OF THE RWY. AFTER 5-10 SECONDS; I OBSERVED AN ACFT ON TXWY H NEAR TXWY B TAXIING IN OUR DIRECTION; THEN MAKING THE U-TURN ON TXWY A AND TAKING OFF ON RWY 10. I BELIEVE WERE LESS THAN 500 FT AGL WHEN THIS ACFT BEGAN ITS TKOF ROLL. I IMMEDIATELY WENT FROM FLAPS 30 DEGS TO FLAPS 40 DEGS FOR SOME MARGINAL SLOWING. I FELT TRAPPED. I FELT GOING AROUND WAS THE MORE HAZARDOUS CHOICE OF A GAR OR LNDG BECAUSE OF THE CHANCE FOR A CLOSER POINT OF APCH TO THE OTHER ACFT (NEAR MIDAIR) AND THE DANGER OF DROPPING MY 'WAKE' ON IT. I ESTIMATE I WAS LESS THAN 200 FT WHEN THE OTHER ACFT BECAME AIRBORNE. I VOICED MY DISPLEASURE WITH THE TWR SUPVR. I TOLD THE SUPVR THAT HIS LCL CTLR PLACED ME IN A DIFFICULT SIT. HE AGREED AND SAID HE WOULD TAKE LCL DISCIPLINE. I ALSO SAID I WOULD FILE THIS RPT. I DO NOT KNOW WHERE THIS PLANE WAS WHEN IT WAS CLRED FOR TKOF; BUT OBVIOUSLY IT WAS NOT IN A POS TO TAKE OFF IMMEDIATELY. THE TWR SHOULD HAVE CANCELED THAT ACFT'S TKOF CLRNC; OR HE SHOULD HAVE DECLINED IT.