PHOENIX (AP) - Opponents of Arizona's new universal private school voucher program should find out early next week if their effort to block the bill until voters can weigh in has been successful.

Maricopa County election officials say they expect to finish checks of nearly 4,000 signatures on Tuesday. Ten of the 15 other counties have already completed their check of a random 5 percent sample of the 111,000 signatures that passed an initial state review.

The counties that have finished confirmed more than 85 percent were valid. Backers need just a 70 percent rate to block the expansion until the November 2018 election.

Voucher backers say they give parents more choice. They've filed two lawsuits seeking to throw out the voter referendum effort, although they've thrown out one.

Opponents argue vouchers siphon money from cash-starved public schools.