Iowa Senator Joni Ernst slammed the State Department on Monday for going "radio silent" on her staffers after they attempted to submit evacuation requests for U.S. citizens and allies trapped in Afghanistan. 

"We’re going through this process of submitting names and I know there was about a day and a half where my staff told me the State Department had gone radio silent—they weren’t receiving messages back," Ernst told "The Faulkner Focus."

"That is absolutely unacceptable. If they need additional people working at the State Department they darn well better get them on board now so we can process all of these requests." 

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The rapid and chaotic nature of the Afghanistan evacuation has made it difficult to precisely pinpoint who still needs safe passage out of the country and how many of them remain.

Ernst said that many people have been calling their local officials in order to send word to the State Department to identify who still needs to be evacuated from Kabul.

President Biden's National Security Adviser Jake Sullivan on Sunday admitted that the administration still does not know how many Americans are in Afghanistan.

"We cannot give you a precise number," Sullivan said. "We believe it is several thousand Americans who we are working with now to try to get safely out of the country."

He then blamed Americans for not registering or deregistering properly at the U.S. Embassy in Kabul for why they do not know the exact number.

Last week, Pentagon spokesman John Kirby said, "I don't know" in response to the same question and then was pressed again in a follow-up question asking how the Biden administration doesn't know these numbers.

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Similarly, State Department spokesperson Ned Price on Friday refused to pinpoint the number of Afghan evacuees expected to leave Kabul by the Aug. 31 withdrawal deadline.

The Pentagon said earlier this week it hopes to evacuate 5,000 to 9,000 people a day in order to meet its objective in getting all Americans and Afghan allies out of Kabul within the president's timetable. 

Fox News' Cameron Cawthorne and and Caitlin McFall contributed to this report.