White House trade adviser Peter Navarro speaks during a briefing on the coronavirus pandemic in the press briefing room of the White House on March 27, 2020 in Washington, DC.
CNN  — 

Amid reports of growing tension between the White House and the Centers for Disease Control and Prevention, White House trade adviser Peter Navarro slammed the top health agency on Sunday, saying “it let the country down” on testing.

“Early on in this crisis, the CDC, which really had the most trusted brand around the world in this space – really let the country down with the testing. Not only did they keep the testing within the bureaucracy they had a bad test and that set us back,” Navarro said on NBC’s “Meet the Press.”

Navarro’s critique is the most critical an administration official has been willing to be on-the-record in blaming the CDC for the faulty testing at the beginning of the coronavirus outbreak in the United States.

A senior official from the CDC on Sunday expressed anger and frustration in reaction to Navarro’s scathing criticism of the agency’s Covid-19 testing response.

“We should remind Mr. Navarro that the CDC is a federal agency part of the administration. The CDC director is an appointed position, and Dr. (Robert) Redfield was appointed by President Trump. If there is criticism of the CDC, ultimately Mr. Navarro is being critical of the president and the man who President Trump placed to lead the agency,” the official told CNN’s Nick Valencia.

Earlier Sunday, a spokesman for the CDC declined to comment when reached by CNN.

Contamination in manufacturing the CDC test for the coronavirus caused weeks of delays that slowed the US response to the pandemic, multiple health officials told CNN last month. The problem stemmed in part from the CDC not adhering to its own protocols, according to a US Food and Drug Administration spokesperson.

The government has never fully explained what stalled the roll out of a crucial test needed to begin measuring the extent of the spread of Covid-19. It would take until the end of February to correct.

But in an interview with Margaret Brennan on CBS’ “Face the Nation” on Sunday, Health and Human Services Secretary Alex Azar admitted to problems with the CDC’s original test while defending the agency.

“The CDC had an issue as they scaled up manufacturing of tests to get them out to about 90 public health labs,” Azar said.

“There was apparently a contamination at an end stage there on the third part of the reagent that never led to false negatives or false positives, but that prevented some of the scale up for a couple of weeks,” Azar said, appearing to confirm earlier CNN reporting pointing to the contamination.

But Azar said “that was never going to be the backbone of testing – broad, mass testing in the United States.” Private companies, not the CDC, would be responsible for that scale-up, he said.

“I don’t believe the CDC let this country down,” Azar later added when asked about Navarro’s comments. “I believe the CDC serves an important public health role, and what was always critical was to get the private sector to the table.”

Navarro’s comments on Sunday come as CNN reported that tensions are rising between the White House and the nation’s leading public health agency. In interviews, senior administration officials in Washington as well as top officials at the CDC in Atlanta described a growing sense of mistrust and animosity between the White House and CDC over how quickly the US should reopen and how the government tracks data on the virus.

In particular, Dr. Deborah Birx, coordinator for the President’s coronavirus task force, has become increasingly critical of the CDC, making clear in recent meetings that she is more than frustrated with the agency, according to two senior administration officials. Specifically, Birx believes the way the CDC gathers data on the coronavirus is antiquated, causing inaccurate and delayed numbers on both virus cases and deaths.

Birx has expressed her agitation during recent task force meetings, where at least one conversation between her and CDC Director Robert Redfield has grown heated, according to a source close to the task force.

Birx and Redfield have known each other for decades, due to their work on HIV research together. And while Birx defended Redfield to their peers earlier this year over the CDC’s faulty test kits, her tone toward him has shifted dramatically in recent weeks, according to multiple officials and a source close to the task force.

This story has been updated to include statements from a senior CDC official and Health and Human Services Secretary Alex Azar.

CNN’s Sara Murray contributed to this story.