Macau was preparing to slash in half the amount of cash China UnionPay bank card holders can withdraw from ATM machines in the city, the South China Morning Post reported, citing a finance industry source, sending shares of U.S. casino operators down.

Macau accounts for a substantial portion of U.S. casino operators' annual revenue. The move would cut the daily withdrawal limit to 5,000 patacas from 10,000 currently, and is expected to take effect from Saturday, the newspaper reported. (bit.ly/2hpKhHI)

China UnionPay is the Chinese government-supported payment card network.

Shares of Melco Crown Entertainment Ltd. were down 12.5 percent at $17.18. Wynn Resorts Ltd. fell 10 percent, MGM Resorts International fell 4.7 percent and Las Vegas Sands Corp. was down 12.3 percent.