Michael Flynn’s attorney claimed in court filings Friday that the Justice Department is withholding critical documents necessary for the defense of her client, as the former national security adviser's legal team wrangles with prosecutors over a sentencing date.

Those filings revealed that Flynn's cooperation with the government is now complete, though a date for his long-delayed sentencing has yet to be agreed upon. Flynn attorney Sidney Powell, whom he retained earlier this summer after firing his old legal team, said her client has “cooperated extensively” with the government as part of the Russia investigation and another probe related to lobbying for the Turkish government.

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“This cost Mr. Flynn more than 100 hours of his time and hundreds of thousands of dollars in additional legal fees,” Powell wrote. “He even waived the attorney-client privilege and the protection of the work-product doctrine to enhance his cooperative effort.”

Flynn pleaded guilty to providing false statements to the FBI during his January 2017 interview about his contacts with the former Russian Ambassador Sergey Kislyak, as part of former Special Counsel Robert Mueller’s Russia investigation. After months of delays, the government said in Friday's joint status report that the case is ready for sentencing, requesting a sentencing hearing between late October and mid-November.

But Powell argued that the case is still “not ready for sentencing,” citing her position as “new counsel” and their timeline of receiving necessary files and documents. Powell requested an additional 90 days before the next status report.

Powell further claimed in the filing that the government “continues to deny our request for security clearances,” requesting the “intervention” of the court after hitting a “dead end.”

Flynn’s legal team had sought security clearances in order to review classified material pertaining to him, including transcripts and recordings of the phone calls that “supposedly underpin the charges against Mr. Flynn.”

The judge in the case, Emmet Sullivan, on Friday scheduled a status conference for Sept. 10 in the trial. He also ordered the Justice Department to produce all evidence "favorable to Flynn and material either to Flynn's guilt or punishment."

In June, a federal judge ruled that the Justice Department did not have to publicly file a transcript of a phone call between Flynn and Kislyak, after previously directing prosecutors to release details of the December 2016 phone call in which Flynn discussed sanctions with the Russian ambassador. Powell pressed anew on Friday for access to the documents.

“The Inspector General of the Department of Justice has completed one or more relevant reports that include classified sections, and he is completing additional reports that reportedly will include a large classified section—a significant portion of which will almost certainly relate to Mr. Flynn,” Powell wrote. “We must have access to that information to represent our client consistently with his constitutional rights and our ethical obligations.”

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Powell also argued that the FBI has yet to share the original draft of Flynn’s FBI interview summary, from Jan. 24, 2017.

Powell’s filing refers to an investigation being led by Justice Department Inspector General Michael Horowitz related to abuses of the Foreign Intelligence Surveillance Act (FISA).

The government, though, argued that they are “not aware” of any classified information that would require a disclosure to them.

Mueller’s office, last year, recommended a lenient sentence for Flynn, with the possibility of no prison time, stating that he had provided “substantial” help to federal investigators about “several ongoing investigations.”

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Now representing the government in the Flynn case is former Mueller deputy Brandon Van Grack; U.S. Attorney for the District of Columbia Jessie Liu; and Assistant U.S. Attorneys Deborah Curtis and Jocelyn Balantine.

Fox News' Bill Mears and Gregg Re contributed to this report.