Leading U.S. infectious disease expert Anthony Fauci on Tuesday warned Congress that while the federal government is working to help manufacture a vaccine against the new coronavirus, its development “might take some time” to come to market.

As a result, Fauci told a Senate health committee in prepared testimony, the nation’s efforts to battle the deadline virus and the COVID-19 disease it triggers should be “focused on the proven public health practices of containment and mitigation.”

In remarks to the New York Times before the hearing, Fauci warned that moving too quickly to ease restrictions on business and social life will put lives at risk from the coronavirus pandemic and hamper the economic recovery.

Fauci was expected to tell a U.S. Senate committee that states should not forge ahead without first meeting administration guidelines for 14 days of declining cases, the New York Times reported, citing an email from Fauci.

“If we skip over the checkpoints ... we risk the danger of multiple outbreaks throughout the country,” the newspaper quoted Fauci, the director of the National Institute of Allergy and Infectious Diseases, as saying. “This will not only result in needless suffering and death, but would actually set us back on our quest to return to normal.”

Fauci was set to appear on Tuesday at the Republican-controlled Senate committee on health, education, labor and pensions after the White House blocked the 79-year-old infectious disease expert from testifying to a Democratic-controlled House of Representatives panel, calling it “counterproductive.”

“All roads back to work and back to school run through testing and that what our country has done so far on testing is impressive, but not nearly enough,” Lamar Alexander, the Republican chairman of the Senate committee, said in an opening statement to Tuesday’s hearing.