B757 DEPARTING FROM ORD RWY 32L; DELAYED ROTATION TO AVOID CONFLICTING ARR TFC ON RWY 9L.

Narrative

TWR TOLD US THAT ACR WAS ONLY XING RWY 32L AT TXWY M AND TOLD US TO TURN TO 330 DEGS AFTER TKOF; AND CLRED US FOR TKOF FROM RWY 32L AT T10. I ASKED THE FO TO VERIFY THE TKOF WAS FOR US. TWR CONFIRMED IT AND THE FO REPEATED IT. AFTER VERIFYING THE AIRSPDS AT 80 KTS AND LOOKING AT THE ENG INSTS; I LOOKED DOWN THE RWY. AT THAT TIME; JUST CLRING THE POST BTWN THE SIDE WINDOW AND THE WINDSHIELD; WAS AN RJ ON APCH TO RWY 9L. I OBSERVED THE RJ FOR A MOMENT AND I WAS NOT CERTAIN WHETHER THE RJ WOULD PASS IN FRONT OF US OR NOT. I TOLD THE FO TO DELAY HIS ROTATION UNTIL WE PASSED THE RJ. ONCE WE WERE CLR OF THE RJ; THE FO ROTATED AND WE DEPARTED. I ASKED FOR THE TWR NUMBER BEFORE SWITCHING TO DEP. IN MY JUDGEMENT; IF WE HAD ROTATED NORMALLY; THE RESULT MIGHT HAVE BEEN DIFFERENT. SUPPLEMENTAL INFO FROM ACN 620932: TWR STATED 'ACR X; ACR Z CROSSING DOWNFIELD; FLY HDG 330 DEGS; RWY 32L FROM T10 YOU ARE CLRED FOR TKOF.' AFTER 80 KTS; CAPT NOTICED AN RJ ON SHORT FINAL FOR RWY 9L ON A CONVERGING COURSE WITH OUR PATH. I DELAYED ROTATION TO AVOID THE ACFT.