(CNN) The US Centers for Disease Control and Prevention says it's developing a system to track the total number of people in the United States tested for the novel coronavirus and it hopes to post that information online -- but that plan is "wholly inadequate," according to US Rep. Mark Pocan, who wrote a letter of complaint to the federal agency this week.

For weeks, the CDC posted on its website the number of people who had been tested for the novel coronavirus, but the number disappeared on Monday.

"All of a sudden those stats vanished," said Pocan, a Wisconsin Democrat.

On Tuesday, a CDC spokeswoman said the agency was trying to gather state testing data and might share it on the CDC website.

"We're working on a system to get [novel coronavirus] test results from state and local public health labs each week and hope to post that," CDC's Kristen Nordlund wrote to CNN.

Pocan told CNN that this plan was "more of an excuse than an answer."

"It's continuing to be the slow-walking response they've been having on this," Pocan said. "We need to get tests out now and we need to get results now and if you're not keeping track, how do you have a national strategy?"

On Tuesday morning, the agency explained to CNN why it had stopped reporting the total number of people being tested for the virus.

"Now that states are testing and reporting their own results, CDC's numbers may not represent all of the testing being done nationwide," CDC spokeswoman Belsie Gonzalez wrote.

But Pocan responded that the CDC keeps track of national health data for a wide range of diseases and should be able to keep track of testing data for the novel coronavirus on a daily basis.

"There's only 50 states. We can get this information relatively easily," he said.

When the outbreak began in mid-January, the CDC was the only lab able to test for the novel coronavirus. On February 5, the agency announced that the test was being distributed to state, county and city public health labs in the US.

A week later, the CDC explained the test kits weren't working as expected, leading to inconclusive results.

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The CDC sent out revised instructions, and last week a handful of labs were able to perform test. This week, the CDC sent out more test kits, and now more public health labs are testing for the virus.

Eventually, a "significant portion" of the testing will be done by private labs, according to Nordlund, the CDC spokeswoman. She did not say if the CDC will be reporting on those testing numbers.