Rep. Adam Schiff, the chairman of the House Intelligence Committee, just tweeted that the whistleblower's attorney has informed the committee that he would like to testify.

The testimony, he said, could happen as soon as this week.

About the whistleblower's complaint: CNN had earlier reported, citing a source familiar with the case, that the complaint was prompted by concerns over communications between the President and a foreign leader. The alleged whistleblower didn't have direct knowledge of the communications that partly prompted the complaint to the inspector general, an official briefed on the matter told CNN on Thursday. Instead, the whistleblower's concerns came in part from learning information that was not obtained during the course of their work, and those details have played a role in the administration's determination that the complaint didn't fit the reporting requirements under the intelligence whistleblower law, the official said.