CAPT OF ACR FLT TAXIES WITHOUT SALUTE FROM TUG DRIVER; CAUSING TUG DRIVER TO SCRAMBLE FOR SAFETY.

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FLT PUSHED BACK FROM GATE APPROX 45 MINS LATE DUE OIL LEAK ON #1 ENG. TUG OPERATOR CLRED ME TO START BOTH ENGS. DURING ENG START; TUG OPERATOR ANNOUNCED DISCONNECTING HEADSET (NORMAL SOP). DURING WHAT SEEMED IN RETROSPECT; AN INORDINATELY LONG DELAY AFTER HEADPHONE DISCONNECT; I NOTICED FO CALLING FOR TAXI CLRNC FROM ATC. I INCREASED VOLUME ON MY COM PANEL IN ORDER TO MONITOR GND CTL'S INSTRUCTIONS. I NORMALLY DON'T MONITOR ATC UNTIL AFTER THE PUSHBACK PROCESS. UPON HEARING THE ATC TAXI CLRNC AND SCANNING OUTSIDE THE AIRPLANE (AND SEEING NO CONFLICTS) I RELEASED BRAKES AND INITIATED TAXI. A FEW MINS LATER WE WERE CONTACTED BY COMPANY AND TOLD TUG DRIVER HAD SOME SORT OF TUG PROB AND HAD TO HURRY TO EVADE TAXIING ACFT. I HAD FORGOTTEN TO OBTAIN TUG OPERATOR'S SALUTE AND RELEASE FROM GUIDANCE BEFORE TAXIING. NO INJURIES OR DAMAGE RESULTED. PERFORMANCE FACTORS INVOLVED INCLUDE NATURAL TENDENCY TO RUSH WHEN LATE. ALSO; ADHERENCE TO SOP'S IS ESSENTIAL; AS THE SOP TO REQUEST TAXI CLRNC ONLY AFTER RELEASE FROM PUSHBACK IS THE ESSENTIAL SAFEGUARD AGAINST TUG/OPERATOR DAMAGE OR INJURY.