The senator made the comments during an appearance on Fox News, claiming that the president's new vaccine efforts are a "diversion away from 9/11."
Ms Ernst, a veteran of the Iraq war, has been one of Mr Biden's more vocal critics over the US military pullout in Afghanistan and his broader relationship with the military.
She falsely claimed on Wednesday that Mr Biden never expressed gratitude or empathy toward American troops overseas in a CNN interview with Jake Tapper.
"As I visit with other veterans, as I have talked to those Gold Star spouses, those Gold Star families, many feel that they have been left behind. They're not even part of a discussion anymore. And what I have not heard from this president is a thank you to those veterans who have served in the global war on terror," she said.
"Not once has he expressed empathy and gratitude to the men and women who have put the uniform on and have fought so bravely overseas the last 20 years to keep our homeland safe. And I feel that by not acknowledging his gratitude for them, he's diminishing their service."
Tapper pushed back on that claim, stating that he had heard Mr Biden make those comments in the past.
"Just as a factual matter, I have heard him talk about this," Tapper said.
Ms Ernst acknowledged that the president may have made the comments outside of her knowledge, and admitted that she has heard him acknowledge US troops, but "not over the greater global war on terror."
CNN emailed Ms Ernst's spokeswoman Kelsi Daniell, pointing out numerous instances in which Mr Biden thanked troops and acknowledged their work, but Ms Daniell brushed the comments off as "platitudes."
Ms Ernst did not make clear exactly why Mr Biden would want to distract the nation from 9/11, as the attack and subsequent wars all occurred or began under Republican presidential administrations.
She recently wrote an editorial for Fox News regarding the legacy of 9/11, arguing the war in Afghanistan made America "stronger."
"For 20 years, the coalition we led into Afghanistan endured, aligned to a common goal. For two decades, the heroism, devotion, and commitment of our servicemen and women, diplomats and humanitarians prevented al Qaeda and their sponsors from achieving their dreams of repeated attacks," she wrote. "An entire generation of Afghan women and girls has experienced the rare freedoms that are so common to us."
In her piece she called the withdrawal from Afghanistan "chaotic and catastrophic."
As for her claims that Mr Biden is trying to distract from 9/11, the president is scheduled to visit all three attack sites – the 9/11 memorial in New York City, the Pentagon in Washington, DC and the Flight 93 memorial in Shanksville, Pennsylvania – over the weekend of the 20 year anniversary.
Mr Biden recently announced sweeping new federal vaccine requirements which will affect nearly 100 million Americans, including private sector employees as well as healthcare workers and federal contractors.
The new rules will force any employer with more than 100 workers to require them to be vaccinated or take weekly Covid-19 tests. That rule will affect nearly 80 million Americans. Any workers at health facilities receiving federal Medicare or Medicaid funding will also have to be fully vaccinated.
Mr Biden is also requiring that all employees of executive branch contractors who do business with the federal government be vaccinated, with no avenue for opting out.
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