WASHINGTON, May 12 (Xinhua) -- Anthony Fauci, a top expert on infectious diseases in the United States, warned on Tuesday that states would face "really serious" consequences if they open up prematurely during the coronavirus pandemic.

"My concern is that if some areas, city, states or what have you, jump over those various checkpoints and prematurely open up without having the capability of being able to respond effectively and efficiently... we will start to see little spikes that might turn into outbreaks," Fauci told a Senate panel during a teleconference hearing.

"The consequences could be really serious," said Fauci, also a key member of the White House coronavirus task force.

Even states that are acting properly in reopening could see a rise in coronavirus cases, according to Fauci.

"Even under the best of circumstances, when you pull back on mitigation, you will see some cases appear," Fauci said. "It's the ability and the capability of responding to those cases with good identification, isolation and contact tracing will determine whether you can continue to go forward, as you try to reopen America."

He also warned that it is "entirely conceivable and possible" that a second wave will happen this fall.

His remarks came as the United States is debating whether it is safe for states to reopen.

Robert Redfield, director of the U.S. Centers for Disease Control and Prevention, said during Tuesday's hearing that the nation must have an extensive capacity to test for the coronavirus before it can lift certain restrictions.

"Rapid, extensive and widely available, timely testing is essential to reopening America," Redfield said.

Brett Giroir, assistant secretary for health at the U.S. Department of Health and Human Services, and Stephen Hahn, commissioner of the U.S. Food and Drug Administration, also gave their testimonies.

More than 1.3 million people have been infected with the coronavirus in the United States, with over 81,000 deaths, according to a count by Johns Hopkins University.