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WASHINGTON, June 23 (Xinhua) -- The U.S. government's top infectious disease expert Anthony Fauci said Tuesday he remains "cautiously optimistic" that there will be a COVID-19 vaccine at the end of this year or early 2021.

Fauci, director of the National Institute of Allergy and Infectious Diseases, made the remarks while testifying at a House committee, along with other senior health officials.

Fauci said he believes "it will be when and not if" there will be a COVID-19 vaccine.

He expressed his concern about rising community spread in some states. "The next couple of weeks are going to be critical in our ability to address those surges," Fauci said.

The country will be doing more testing, according to Fauci.

The testing issue became controversial after U.S. President Donald Trump told rallygoers over the weekend that he asked staff to slow down coronavirus testing as it was uncovering too many infections.

More than 2,325,000 COVID-19 cases have been reported in the country with the fatalities surpassing 120,700 as of Tuesday afternoon, according to a tally by Johns Hopkins University.

Many states, including Alabama, Arizona, Florida, South Carolina and Texas, had reported either new single-day highs or set a record for seven-day new case averages.