"Look, we've been completely cooperative throughout this entire process", Sanders said.
He added that there was "zero" chance that Trump Jr. did not introduce the lobbyists to Trump.
In a separate investigation into Russian interference in the 2016 presidential election, led by Mr Mueller, Mr Bannon will meet with investigators for an interview instead of appearing before a grand jury.
The report, cited by "four sources with direct knowledge of the confidential proceedings", said that shortly after his confession Bannon suddenly became tight-lipped when it came to any further information.
Bill Burck, a lawyer for Mr Bannon, could not immediately be reached for comment. The experts also said it could be a signal to Bannon, who has tried to publicly patch up his falling-out with the president, that despite Trump's legal threats, Bannon must be completely forthcoming with investigators.
"Bob Mueller is running the show", Napolitano said. "Testifying before a grand jury is intimidating", Mariotti wrote on Twitter. It could also signal that Mueller is seeking to pressure Bannon to agree to an interview with his investigators. He arrived with no documents, saying that if lawmakers wanted emails and other communications, they were likely to be available from other witnesses.
The official declined to say who initiated the mid-testimony phone call or who took part on behalf of the White House.
Bannon reportedly invoked executive privilege, telling the committee that he couldn't answer their questions about anything he was involved with after the election because he'd been advised not to by the White House. "It goes well beyond anything we've seen in this investigation ..."
But sitting White House officials rarely appear before the congressional panels investigating Russian Federation meddling, making Hicks' appearance even more significant - especially given her ties to the President. "So this obviously can't stand". Trump, at the same time, needs Bannon, his strongest link to the populist right.
Schiff told MSNBC later that Bannon had refused to answer questions about conversations held both during his time at the White House and during the transition between the election and Trump's inauguration. "We've been cooperating fully with these ongoing investigations and encourage the committees to work with us to find an appropriate accommodation in order to ensure Congress obtains information necessary to its legitimate interests".
As a result the chairman, Republican Devin Nunes, issued a congressional subpoena, spokesman Jack Langer said. Bannon left his position as chief strategist at the White House last August. CNN reported that Bannon would answer Mueller's questions because executive privilege would not then apply.
Those key elements bear directly on the criminal investigation now underway by special counsel Robert Mueller, who is charged with investigating ties between the Trump campaign and Russian Federation and whether the president obstructed justice by firing Comey or by taking other actions to thwart investigators.
Representative Mike Conaway (R-Texas) told WNBC the committee's subpoena remains in effect and described the interview as in "recess".