During the daily White House coronavirus press briefing early last week, President Trump praised the country’s testing regimen for the virus.

“We have now done 1,790,000 tests nationwide,” Trump said. “That’s more than any other country in the world, hence we have more cases. And that number is growing by nearly 125,000 people per day. Think of that one. So it’s growing by 125,000 people per day.”

“I told you about South Korea,” he added. “This is a, you know, vastly faster — and we also have, they say, the most accurate of tests.”

The mention of South Korea was an attempt to contrast the United States’ testing with testing in a country that has been seen as having contained the coronavirus through broad testing. The virus was detected in both the United States and South Korea at the same time, but, for a variety of reasons, including testing, South Korea better contained the virus’s spread within its borders.

Testing in the United States was delayed significantly for weeks, thanks in part to a decision for the government to build its own test. When that test ran into problems, it severely limited the number of tests that could be conducted. The Post reported last month that only a few thousands tests from the Centers for Disease Control and Prevention were conducted by Feb. 28 — compared with tens of thousands of tests that had been completed in South Korea.

Over time, that changed. By mid-March, the number of tests being completed each day was increasing exponentially, according to state data compiled by the Covid Tracking Project.

As it turns out, though, Trump’s confidence in the U.S. testing process wasn’t as solid as he presented last week. Reuters reported on Monday morning that South Korea would send 600,000 of its own test kits to the United States this week after Trump specifically requested them last month. The White House has consistently claimed that millions of test kits were available for testing, often conflating that figure with the number of tests that were expected to be completed. The order from South Korea is curious for two reasons: It contradicts Trump’s claims about the supremacy of U.S. tests, and it suggests a lack of supply, at least at that time.

The request came at an interesting moment in the testing process. Throughout March, the number of tests that had been completed kept climbing upward exponentially (note the slope on the first dashed line below). In late March, that increase slowed (second dashed line).

In fact, the number of daily tests catalogued by the Covid Tracking Project has been flat over the past week or two. Trump touted the completion of 125,000 tests per day on April 6, a day on which about 150,000 tests were completed, according to the Tracking Project’s data. Over the past seven days, the number of tests added has averaged 147,000 per day.

Looking at the daily tests being completed on a logarithmic graph, the inflection point in late March seems clear.

Some of the reasons for the slowdown are primarily administrative. The San Francisco Bay area has a testing system in place run by Verily, a company that’s part of Alphabet, the parent company of Google. During a news briefing last month, Trump announced that the Verily program would bring screening and testing to the entire country. As of writing, though, it covers only a handful of counties. What’s more, a spokesperson for the company told The Post that even the existing sites aren’t operating at full capacity, limited to about 200 tests a day by the office of Gov. Gavin Newsom (D-Calif.) in order “to keep capacity sustainable while minimizing risk to healthcare professionals delivering acute care.”

The mention of risk to those administering tests raises a more urgent reason for the limit on tests: shortages of supplies. In some places, there have been reports of limited availability of protective equipment. Even at a drive-through test facility, the employees conducting the tests often wear full protective equipment to minimize exposure from possibly infected individuals.

The shortages go further than that. New York City has announced that it is running low on test swabs, the long Q-Tip-like devices used to take samples from patients. The Seattle Times reported on similar shortages in that area.

“We can do more testing than what we are doing,” an official at one lab told the paper. His lab was operating at less than 40 percent capacity. The lack of swabs and other material was “an important bottleneck.”

The administration has talked about deploying a self-swab, which would solve both problems at once: allowing people at drive-through test sites to take their own samples within their cars, reducing the need for protective equipment for employees and increasing the number of swabs available. So far, though, self-swabs haven’t been issued.

All of this is of critical importance as the White House debates rolling back social distancing efforts. To allow the economy to reopen even partially, the country will need to track and contain outbreaks of the virus — something that requires an ability to conduct broad, rapid tests. Over the past two weeks, the data suggest that our ability to establish such a system has become less likely, not more.