A B767-300 Captain taxiing for takeoff at experienced a runway incursion when he misinterpreted a taxi clearance. The distraction of copying the ATC enroute clearance was a factor.

Narrative

I was the Captain of Part 121 US Military Charter flight; a B767-300; from Kuwait City; Kuwait. The First Officer and myself went through preflight checks; started up and were given instructions to taxi to Runway 33L for takeoff. We attempted to get our ATC clearance early in our taxi but we told to expect it on W1 (the parallel taxiway to Runway 33L). As we approached the holding point for Runway 33L we were given our clearance followed by an amendment to it. As we were verifying the amendment the Controller instructed us 'call when ready; 33L hold.' What I thought I heard was '33L position and hold.' As the First Officer configured the cabin altitude control panel and switched the pack selectors to off in order to adhere to our aircraft performance data requirement for our weight and temperature for Runway 33L; I verified the final approach appeared clear and continued to taxi into 'position and hold'. Just as the nose of the aircraft crossed the runway edge the First Officer yelled 'hold short'! The Controller asked us to 'hold our position'. Several seconds later we were cleared for takeoff. Receiving ATC clearance at such a late phase of ground operations is a contributing factor. This is common in some countries; I think receiving a clearance at the gate prior to taxiing is a safer action. Adherence to ICAO phraseology such as 'line up and wait' needs to be stressed around the world. Myself and the copilot had to many distractions at that critical phase of operation.