NBC's Brian Williams has been anchoring the news from South Africa, but he will not be joined by either Scott Pelley or Diane Sawyer. 

The AP writes that ABC and CBS are keeping top anchors Diane Sawyer and Scott Pelley in New York, where George Stephanopoulos will also be located Tuesday when he anchors an early morning ABC special on Mandela. The moves show how economics and a dwindling interest in international news are changing the biggest broadcast networks, where a decade ago there would have been little question that their most prominent faces would be on hand for such a big story.

‘‘We agreed here that this is a moment in history and he needed and wanted to be there,’’ said Patrick Burkey, executive producer of Williams’ ‘‘Nightly News.’’ ‘'We spent a whole lot more time figuring out how to do it than whether or not we should.’’

It was particularly important to Williams, who interviewed Mandela shortly after he was released from a South African prison, he said.

The only other time Williams has anchored from overseas in 2012 and 2013 was surrounding the London Summer Olympics, for which NBC was the exclusive rights-holder in the United States, said Andrew Tyndall, a consultant who tracks evening news content.

Both Pelley and Sawyer reported from Rome this year on the selection of a new pope. Pelley also anchored a night from London last year, though it wasn’t clear why he was there, Tyndall said.

All three of the news broadcasts have cut back on foreign coverage, with that trend most apparent in anchors’ travels, he said.

More on the story from The AP