Brian Williams, acknowledging that the scrutiny and criticism he was attracting was becoming a distraction for his network, said on Saturday that he was stepping aside as anchor of NBC’s “Nightly News” for the next several days.

In a memo to the NBC News staff, Mr. Williams said that Lester Holt, the anchor for “Dateline,” would step in as the network dealt with the crisis caused by Mr. Williams’s admission that he had misled the public with an account of a helicopter incident in Iraq.

“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,” Mr. Williams said in the two-paragraph memo.

Mr. Williams is both anchor and managing editor for “NBC Nightly News.”

Mr. Williams did not say exactly when he expected to return to the anchor chair. “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 said.