President Barack Obama believes FBI Director James Comey is a man of integrity and is not trying to influence the U.S. presidential election by announcing scrutiny of additional emails linked to Democrat Hillary Clinton's private server, the White House said on Monday.

White House spokesman Josh Earnest also said he has no "independent knowledge" of how Comey had arrived at his decision to make public the FBI email investigation or "what factors were considered" in his decision to discuss the issue publicly.