Brian Williams said he is temporarily stepping away from the "NBC Nightly News" amid questions about his memories of war coverage in Iraq, calling it "painfully apparent" that he has become a distracting news story.

In a memo Saturday to NBC News staff that was released by the network, the anchorman said that as managing editor of "NBC Nightly News" he is taking himself off the broadcast for several days. Weekend anchor Lester Holt will fill in, Williams said.

NBC News refused to comment Saturday on when or whether Williams would return and who would decide his future.

Williams, however, said he would be back.

"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 his memo.

"Upon my return, I will continue my career-long effort to be worthy of the trust of those who place their trust in us," he wrote.

NBC News President Deborah Turness said Friday that an internal investigation had been launched after questions arose over Williams' false on-air statements that he was in a helicopter hit by a rocket-propelled grenade while in Iraq in 2003. Williams apologized for those statements Wednesday.