The White House is acknowledging for the first time that officials did direct key documents be filed in a separate classified system.

In a statement provided to CNN, a senior White House official says it was under the direction of National Security Council attorneys: "NSC lawyers directed that the classified document be handled appropriately."

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CNN journalists say the admission lends further credibility to the whistleblower complaint description of how the transcript with the Ukrainian president, among others, were kept out of wider circulation by using a system for highly sensitive documents.

The statement does not explain whether anyone else in the White House was part of the decision to put the documents in the more restrictive system.