Question: You’ve been given a clearance to taxi to the end of a runway for departure. The runway is 6,000 feet long with several intersections. While you are taxiing, ATC instructs you to taxi to one of the intersections instead of the end of the runway. You realize this would reduce the available runway length to 3,000 feet. Must you accept the intersection departure?
Answer: No. If the pilot prefers to use the full length of the runway, or a different intersection, the pilot is expected to notify ATC accordingly. The pilot is ultimately responsible for ensuring there is enough runway available for a safe departure. Source: AIM Chapter 4-3-10