The United States "desperately" needs more tests to screen for the new coronavirus, a public health expert told Congress on Friday.

"Testing capacity is not currently adequate, and we need more," said Dr. Lisa Maragakis, senior director of infection prevention for the Johns Hopkins Health System and an epidemiologist. "We need this as soon as we can have it."

Maragakis' remarks were part of a briefing on Capitol Hill by five experts from Johns Hopkins, which has been tracking the international outbreak.

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Around the world, the virus has sickened about 100,000 people and killed more than 3,000. While other countries have run tens of thousands of tests — South Korea has tested more than 100,000 patients — the U.S. has tested barely a fraction of that. Technical glitches and narrow criteria for who could be tested initially hampered the efforts.

The test kit's technical problems have since been resolved and the Centers for Disease Control and Prevention guidelines expanded. And while testing capacity has increased, promises made by the Trump administration have yet to come to fruition.

"We have more than 2,500 kits that are being distributed around the country this week that will make more than 1.5 million tests available at hospitals that have requested them, and in areas of the country that have been particularly impacted by the coronavirus," Vice President Mike Pence, who is overseeing the Trump administration's response to the coronavirus crisis, said during a meeting Wednesday with diagnostic lab CEOs.

Pence's comments came two days after Food and Drug Administration Commissioner Stephen Hahn predicted kits for "close to a million" tests would be usable by the end of the week.

But Thursday, Pence backtracked and said that that goal had been moved to next week.

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"We don't have enough tests today to meet what we anticipate will be the demand going forward," he acknowledged.

Still, there has been progress with getting test kits into laboratories.

The initial test used in America for the never-before-seen coronavirus was developed by the CDC. The new test kits are manufactured by Integrated DNA Technologies, Inc., which told NBC News in a statement Friday afternoon that it had delivered enough kits to test more than 700,000 individuals using the CDC protocol.

"We continue to work closely with the CDC and FDA to ensure ongoing supply to meet demand and are on track to release additional IDT products on an ongoing basis," the Coralville, Iowa-based company said.

Scott Becker, CEO of the Association of Public Health Laboratories, which represents the 100 local and state public health laboratories qualified by the CDC to do this type of testing, could not confirm how many test kits had been received, but said more labs had received them.

"They've been rolling out and there are many more coming," he said, adding that as of Friday morning, 69 public health labs across 46 states and the District of Columbia had started testing.

Only a handful of public health labs were still waiting to get their new tests delivered, Becker said. Some who just received the test kits were still implementing the verification process to make sure they were working properly in their laboratories, but that process usually only takes a day to complete, he said.

"When we're fully up and running next week, we're going to be able to do 10,000 tests a day."

"When we're fully up and running next week, we're going to be able to do 10,000 tests a day," he said.

Meanwhile, two private commercial diagnostic labs said they had received authorization from the federal government to start testing as well. LabCorp announced that as of Thursday at 6 p.m. ET, it had the ability to start performing several thousand tests per day immediately, with an estimated turnaround time of 3 to 4 days. Quest Diagnostics Inc. said it expected to start testing samples Monday.

Those additions will help significantly, Maragakis told Congress on Friday, as will upcoming testing that Johns Hopkins also expects to make available in the coming days.

"I think all of those individual efforts are to be commended because we desperately need the testing," she said.

"Hopefully we will have — and I think this is probably a matter of weeks, not months — that we would have access to more rapid forms of diagnostic testing that are not so labor intensive as the test we have now," she added.

The need for more testing, plus an investigation into the earlier missteps that prevented widespread testing sooner, was echoed by former CDC chief Dr. Tom Frieden.

"A review should be done to avoid similar problems in the future, but for now the focus is to get tests out, quickly, to all states.”

“CDC is widely trusted because of its transparency and willingness to admit and learn from errors. It’s clear that something went wrong with tests CDC initially sent out for coronavirus. It didn’t go wrong with Zika or H1N1 tests," Frieden, who currently serves as president and CEO of Resolve to Save Lives, an initiative of Vital Strategies, said in an emailed statement to NBC News. "A review should be done to avoid similar problems in the future, but for now the focus is to get tests out, quickly, to all states.”

Becker expected more public health laboratories to gain the ability to test through the weekend. Between those additions and Quest and LabCorp, "that's going to greatly enhance our capacity as a nation to do greater volumes of testing," he said.

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