Tim Morrison, a former White House national security official, told House investigators in sworn testimony that he feared leaks of the contents of the July 25 call between President Trump and Ukrainian President Volodymyr Zelensky would be damaging, so he recommended restricting access to the transcript.

Morrison, an expert on Russia and Ukraine who served on the National Security Council before leaving the job at the end of October, said he knew immediately after listening to the call in which Trump asks Zelensky to investigate former vice president Joe Biden and his son Hunter that they needed to keep it under wraps.

“I recommended to them that we restrict access to the package,” Morrison said, according to a transcript of his Oct. 31 testimony released by the House committees on Saturday.

He said he was “concerned about whether or not they would agree that it would be damaging for the reasons I outlined in my statement if the call package — if the call mem-con or its contents leaked.”

But Morrison said it was a “mistake” that the call transcript ended up transferred to a highly classified system reserved for code-word intelligence rather than the normal “Portal” system that has restricted access.

Even though he feared the conversation leaking, Morrison broke with colleagues in telling House investigators that he heard nothing “improper” on Trump’s call with Zelensky.

Morrison’s interpretation of the controversial call, which sparked the impeachment proceedings, could make him a valuable witness for Republicans, who complained on Friday that Democrats were delaying the release of his testimony.

“In your view there was nothing improper that occurred during the call?” the Republican’s lead counsel asked Morrison.

“Correct,” he replied.

Morrison expressed frustration that Lt. Col Alexander Vindman, one of his subordinates, had gone to the NSC’s top lawyer with concerns about the call in which Trump pressed Zelensky to investigate the Bidens.

He also disputed Vindman’s account in which he asked for edits to the document to include a mention of Burisma, the gas company that employed Hunter Biden on its board.

“I believe it was accurate and complete,” Morrison said of the rough transcript. He said he recalled accepting all of Vindman’s proposed changes. Morrison’s recollection, though, contradicts the notes of Jennifer Williams, a top aide to Vice President Pence, who said that Burisma was mentioned on the call. Williams’s transcript was also made public Saturday.

“The testimony released today shows that President Trump’s July 25 phone call with Ukrainian President Zelensky immediately set off alarm bells throughout the White House,” said Intelligence Chairman Adam B. Schiff (D-Calif.), Foreign Affairs Chairman Eliot L. Engel (D-N.Y.) and acting Oversight Chairwoman Carolyn B. Maloney (D-N.Y.) in a joint statement.

Morrison also testified that between July 16 and Sept. 11, he understood that the U.S. ambassador to the European Union, Gordon Sondland, had spoken with Trump about half a dozen times.

Trump has said he doesn’t know Sondland well and has tried to distance himself from the E.U. ambassador, whom Trump put in charge of Ukraine policy, even though Ukraine is not a part of the European Union.