"This conduct is absolutely unacceptable", she said.
He said she was rude for interrupting another reporter, though he did briefly answer one of Ms Ryan's questions.
Acosta, 47, regularly grills Sanders at press conferences where she defends Trump's most controversial policies. It purportedly shows the moment a White House intern attempted to take a microphone from Acosta during a heated exchange with the president.
However, she is unsuccessful as the reporter manages to keep hold of the microphone, telling her: "Pardon me, ma'am".
"Honestly, I think you should let me run the country and you run CNN", Mr Trump snapped, adding "and if you did it well, you're ratings would be much better".
As you can see in the video, a White House aide tried to grab Acosta's microphone away, but he refused to give it up.
Sanders said Thursday the White House stood by its decision: "The question is: did the reporter make contact or not?"
Press secretary Sarah Sanders says a reporter's access was suspended because he put "his hands on a young woman". "Only they would attack the President for not being supportive of a free press in the midst of him taking 68 questions from 35 different reporters over the course of an hour and a half - including several from the reporter in question".
The White House announced late Wednesday that it is temporarily suspending press credentials from CNN's Jim Acosta.
- Rafael Shimunov (@rafaelshimunov) November 8, 2018Correction: the white house --uploaded a doctored video-- there is no evidence that they are the source of the doctored video.
"This is a lie", Acosta tweeted back at Sanders. "You and I have a difference of opinion", he said.
'I wanted to challenge you, ' Acosta started but Trump interrupted him: 'Here we go.
"A free press is vital to democracy, and we stand behind Jim Acosta and his fellow journalists everywhere".
Acosta tweeted that this was "a lie".
Acosta was denied entrance on White House grounds on Wednesday evening for his nightly segment, and instead, recorded a conversation with a uniformed officer. "Revoking access to the White House complex is a reaction out of line to the purported offense and is unacceptable.We urge the White House to immediately reverse this weak and misguided action".
The move followed an incident during President Trump's Wednesday news conference, in which Acosta challenged Trump about his claims regarding immigrants trekking through Mexico to reach the US border.
Acosta finally relinquished the mic and sat down, but Trump then began to verbally berate him from the lectern.
But many high-profile media members, including The New York Times' Maggie Haberman and CNN executive Matt Dornic, have accused Sanders of using a doctored video speeding up Acosta's arm motion, as evidence.