He added: “But I’ve been very clear with Oklahomans that coronavirus is still in the United States, and it’s still in Oklahoma.”

Interviewed on the same show, Dr. Thomas V. Inglesby of the Johns Hopkins Bloomberg School of Public Health said the pandemic may be reaching an overall plateau, but the risk of a new spike remained clear, and there should be no sense that the nation had turned a corner. “If you go state by state, you see that about half of the country — in half of the country, the numbers are still rising day to day,” he said. “And about another third of the country, there seems to be a leveling off. And only in a minority of the country the numbers are actually coming down day by day.”

He said the virus would be around until there was a vaccine for it. “Everyone needs to be aware that, even as we’re beginning to open up again, there is a clear chance of a rise in cases in states that are doing that.”

Dr. Deborah Birx, the White House coronavirus response coordinator, said Americans should expect social distancing guidelines to continue for months. “Social distancing will be with us through the summer,” she said Sunday on NBC’s “Meet the Press.”

Dr. Birx also said a different type of coronavirus test was required to screen the U.S. population on the necessary scale, saying that it would take “a huge technology breakthrough” to get there. What’s needed, she said, is a screening test that detects antigens, like the screening tests used for flu, strep and other diseases. Antigens stimulate the body to produce antibodies, and are essentially evidence of an immune response.

On CNN’s “State of the Union” Sunday, she also acknowledged that the nation was not using existing testing capacities to the fullest. She said the administration was working with states to identify all their testing sites and supply the needed swabs and chemical reagents.

In Michigan, Gov. Gretchen Whitmer, a Democrat whose coronavirus policies have been the target of protests, extended the stay-at-home order until May 15, but relaxed a number of social distancing policies on Friday to allow in-state travel and some recreational activities.