Tensions escalated Wednesday between the special counsel’s office and the defense lawyers representing a Russian business charged with interfering in the 2016 presidential election, as the two sides disputed whether a recent phone conversation ended with an abrupt hang-up.

During a hearing before U.S. District Judge Dabney Friedrich of the District of Columbia, special counsel prosecutor Jeannie Rhee said Reed Smith partner Eric Dubelier, a defense lawyer for Concord Management and Consulting LLC, hung up nine minutes into a “meet and confer” call that was scheduled to last an hour May 11.