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NEW YORK -- NBC’s Brian Williams is anchoring his nightly newscast from South Africa early this week, covering the world’s mourning for Nelson Mandela, but he won’t have some of his usual company.

ABC and CBS are keeping top anchors Diane Sawyer and Scott Pelley in New York, where George Stephanopoulos anchored an early morning ABC special Tuesday 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.

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

"It was a luxury at a time when they were flush," Tyndall said. "It was never about ratings. It was done for publicity and promotion, to boost the anchors’ prestige and to show that the network was on top of the news."

Competition also played a big part: when Tom Brokaw, Peter Jennings and Dan Rather were the top anchors, if word got out that one of them was traveling to a big story, the other two usually headed to the airport.

Earlier in her tenure, Sawyer traveled to Haiti for an earthquake there and to Japan in the wake of a tsunami, Tyndall noted, and the amount of travel for domestic stories hasn’t changed much.

"Of course, economics play into the decisions," Burkey said. "But for us, if it’s a big story, we want to be there."

Cable news networks are taking different approaches, too. For CNN, anchors Christiane Amanpour, Anderson Cooper and Chris Cuomo are all in South Africa.