Story highlights KT McFarland's confirmation is in doubt over her role during the Trump transition

Foreign Relations Chairman Ben Corker said there is a pause on her nomination

(CNN) Democrats have placed a hold on the nomination of KT McFarland to be ambassador to Singapore until she answers their questions about her knowledge of communications between former national security adviser Michael Flynn and Russian ambassador Sergey Kislyak, a Democratic source told CNN.

The Democratic hold on McFarland's nomination means that Senate Majority Leader Mitch McConnell would have to take procedural steps in order to overcome the hold and confirm her nomination, which would eat up valuable floor time.

Maryland Sen. Ben Cardin, the top Democrat on the Senate Foreign Relations Committee, told CNN he thinks McFarland's nomination is imperiled.

"I think there should be no action on this nomination until we get the information," Cardin said.

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