Oregon will require masks in all indoor public spaces, effective Wednesday, July 1.

Gov. Kate Brown announced the expansion of her mask requirement this afternoon. Oregon had previously required masks in eight counties, including the three largest counties in the Portland metro area.

She cited modeling that showed a looming spike in COVID-19 cases, and warned that if spread of the novel coronavirus doesn't slow, "our hospitals could be overwhelmed by new COVID-19 cases and hospitalizations within weeks."

The statewide mask rule comes after three consecutive days of Oregon health officials reporting more than 200 new COVID-19 cases. On Monday, the state reported 146 new cases.

Nationally, data shows a strong correspondence between requiring masks and limiting the virus's spread. In 11 states that required face coverings, new cases fell by 25% over the past two weeks, The Philadelphia Inquirer reported. In 16 states where masks were merely recommended, cases rose by 84%.

Brown's mask rule did not previously include a legal mechanism for enforcement. But she is now pitching the rule with a threat: Wear one or she'll close restaurants.

"I do not want to have to close down businesses again like other states are now doing," Brown said. "If you want your local shops and restaurants to stay open, then wear a face covering when out in public."

California, Texas and Florida have buttoned up their restaurants and bars in recent days—either closing them entirely or restricting them to outdoor service—in the wake of dramatic COVID-19 case spikes.

Brown conceded over the weekend that if those numbers continue, she'll be forced to again close bars, restaurants and other businesses that just reopened from three months of closures.

Brown hasn't made that choice yet. She described the July 4 holiday weekend as pivotal.

"The upcoming July 4 holiday weekend is a critical point for Oregon in this pandemic, and we can all make a difference," she said. "We saw a lot of new COVID-19 cases following the Memorial Day holiday. Another spike in cases after the upcoming holiday weekend could put Oregon in a dangerous position."