As many as 100,000 Nebraskans would need to enroll in a state-based health insurance exchange before the program could sustain itself as required, according to a report presented to lawmakers Friday.

Nebraska insurance officials can't decide whether to recommend a state-based health insurance exchange or follow a proposed federal model until they know how much the national plan will cost, Nebraska Department of Insurance Director Bruce Ramge said.

Nebraska will not enact a health care exchange mandated by the federal health care overhaul until officials know for sure whether the measure is constitutional, Gov. Dave Heineman said Monday.

Unanswered questions about the new national health care law have slowed Nebraska's efforts to prepare a statewide insurance exchange, state insurance officials said Monday.