The surprise move came after Steve Bannon refused to answer scores of questions about topics
during the transition and his time as President Donald Trump's chief strategist, with Bannon's attorney saying he had been instructed by the White House not to answer those questions over concerns that it could breach executive privilege.
Hicks' appearance Friday was anticipated given her close ties to Trump, which predate the campaign, and the central role she has played through the election season and in the White House.
The committee made the decision to delay Hicks' appearance in order to give investigators time to sort out with the White House what she could and could not discuss, one of the sources said. She is still expected to speak with the panel at a later date.
The White House and an attorney for Hicks did not respond to request for comment.
On Wednesday, White House press secretary Sarah Sanders said the White House was cooperating with the congressional investigations.
"We've been fully cooperative with the ongoing investigations, and we're going to continue to do so," Sanders said. "And we encourage the committees to work with us to find the appropriate accommodation in order to ensure Congress obtains all the information that they're looking for. But there's a process that this works through."
But Rep. Adam Schiff, the top Democrat on the House Intelligence Committee, said the decision to scrap Hicks' testimony is part of a pattern to derail the probe. In addition to Bannon, he pointed to Wednesday's testimony of Corey Lewandowski, the former campaign manager who said he was unprepared to answer many questions about matters that occured after he left the campaign in 2016. He placed the blame on the cancellation of the testimony squarely on the White House.
"Following Mr. Lewandowski's testimony and refusal to answer questions, the administration canceled entirely an interview scheduled for Friday with another key witness in our investigation," Schiff said. "If that interview has been rescheduled, the date has not yet been shared with the minority."