HONG KONG—The Chinese unit of U.S. gambling company MGM Resorts International said it would pump almost $600 million into its Macau casino operator as the company prepares to bid for a new license in the pandemic-battered gambling enclave.

MGM China Holdings Ltd. recorded widening losses in the first half of the year due to Covid-19 outbreaks in mainland China and Macau that the company said have restricted travel to the city. Earlier this month, the Hong Kong-listed company posted a $306 million loss attributable to the owners of the company in the first six months of 2022, deeper than a year-earlier loss of $221 million.