"In the midst of a career spent covering and consuming news, it has become painfully apparent to me that I am presently too much a part of the news, due to my actions," Williams said in a statement posted on NBC News' website.
Williams said he planned eventually to return to the broadcast and "continue my career-long effort to be worthy of the trust of those who place their trust in us."
Lester Holt, who typically anchors NBC Evening News on weekends, will step in to handle the weekday evening broadcast in the interim, Williams said.
NBC, a unit of Comcast Corp, on Friday said it was launching an internal probe of Williams' false statements that he was in a helicopter that was brought down by enemy fire during the U.S. invasion of Iraq.
Williams has admitted that he portrayed the episode inaccurately, but his apology - in which he said he misremembered the incident - provoked widespread derision, with some war veterans calling for his resignation.