Attach -기는어렵겠어요 to a verb stem to decline in a considerate but clear way: 보내기는어렵겠어요, 돕기는어렵겠어요. Here it softens how you state the difficulty, not whether you have agreed.
Situation or form
Korean expression
오늘전체자료보내기
오늘전체자료를보내기는어렵겠어요.
이번주에돕기
이번주에돕기는어렵겠어요.
가능한다른행동
대신내일목차를보내드릴게요.
대안을약속하지않음
지금은다른방법도약속하기어렵겠어요.
When the full document today is not possible but its contents list tomorrow is, separate the refusal and the alternative. A contents list is not the full document. No alternative is required when none is available.