Former White House chief strategist Steve Bannon arrives to testify in the criminal trial of Roger Stone, former campaign advisor to U.S. President Donald Trump, on charges of lying to Congress, obstructing justice and witness tampering at U.S. District Court in Washington, U.S., November 8, 2019. REUTERS/James Lawler Duggan

WASHINGTON (Reuters) - The U.S. government on Friday called one-time White house adviser Steve Bannon to the stand in its trial of President Donald Trump’s former aide, Roger Stone.

Bannon appeared, wearing all black, to answer questions about Stone - a self-described “dirty trickster” and “agent provocateur” - who has pleaded not guilty to charges of obstructing justice, witness tampering and lying to the U.S. House of Representatives Intelligence Committee.