White House coronavirus task force coordinator Deborah Birx is warning of an uptick in coronavirus cases in nine U.S. cities.

“Many of the Sun Belt states have made substantial progress with their mitigation efforts,” Birx told state and local officials on Wednesday, according to a copy of the call obtained the Center for Public Integrity, referring to a slew of Southern states that experienced surges earlier this summer. 

But Birx said that the percentage of coronavirus tests coming back positive is increasing in nine U.S. cities as well as California's Central Valley. 

"We are concerned that both Baltimore and Atlanta remain at a very high level. Kansas City, Portland, Omaha, of course what we talked about in the Central Valley,” Birx said. "We are seeing a slow uptick in test positivity in cases in places like Chicago, Boston and Detroit and D.C.”

Birx also said that Nebraska and California have moved into the red category, with more than 10 percent of tests coming back positive. And she noted that while Los Angeles saw improvements, there was significant movement of the virus up California's Central Valley.

Birx noted that the virus has entered a new phase, “in that it's in both rural and urban areas." 

In another call obtained by the Center for Public Integrity last month, Birx warned of an uptick in 12 other U.S. cities, including Miami, New Orleans, Las Vegas, San Jose, St. Louis, Indianapolis, Minneapolis, Cleveland, Nashville, Pittsburgh, Columbus and Baltimore.