By Kate O'Keeffe 

Sheldon Adelson, the 81-year-old billionaire behind the world's largest gambling company, has a new job. The Las Vegas Sands Corp. chief executive will in March also take on that title at the company's prized Macau unit, according to a Friday statement from Sands China Ltd.

The news, which comes as the once-booming Chinese gambling hub experiences its worst-ever downturn, underscores the octogenarian's unwavering focus on his casino empire and solidifies the control the Las Vegas parent wields over its Macau unit.

Mr. Adelson, who controls Las Vegas Sands, is currently the Las Vegas company's chairman and chief executive. He is also the chairman of Sands China, which is controlled by its Las Vegas parent. On March 6 Mr. Adelson will also become Sands China's chief executive, the Hong Kong-listed unit said in its Friday statement. He will succeed Ed Tracy, Sands China's 62-year-old current chief executive who last week told staff in a letter reviewed by The Wall Street Journal that he would in March return to the U.S. to focus on family and health.

Sands China will also appoint Las Vegas Sands' 59-year-old president, Rob Goldstein, as its interim president effective March 6, the company said in its statement.

The management changes follow a string of recent departures of top executives at Sands China. The Macau unit's general counsel is set to retire in April, and its No. 2 executive left in September 2013 and hasn't been replaced. Senior executives in finance and international marketing have also recently left the company, according to people familiar with the matter.

Deutsche Bank analyst Karen Tang said in a Friday note following the company's announcement: "We are concerned that the frequent senior management re-shuffle could lead to another round of mid-level management departures from the company." This could be a problem given the shortage of talented mid-level managers in Macau, Ms. Tang suggested.

The management changes come at a critical time in Macau, which has suffered a seven-month losing streak. Last year the territory recorded its first annual decline in gambling revenue since data became available in 2002.

Executives and analysts attribute the sharp reversal of fortunes in Macau, which rakes in seven times more gambling revenue than the Las Vegas Strip, primarily to China's crackdown on corruption. In addition to bringing down many top mainland officials, the sweeping campaign has led high rollers to shy away from Macau's baccarat tables, they say.

Las Vegas Sands discussed Mr. Adelson's role at the company last year while it was looking for a replacement for its former president, Mike Leven, who retired in December. Before deciding on Mr. Goldstein, who has been with the company for about 20 years , the company told people involved with the search that the president role could possibly be upgraded to a chief executive role because Mr. Adelson had said he would be willing to cede the title for the right candidate, according to people familiar with the matter. But shortly after the company had given those instructions, Mr. Adelson changed his mind, the people said.

Company spokesman Ron Reese in May told the Journal, which had contacted Las Vegas Sands for comment about the search, that Mr. Adelson wouldn't cede the title.

To a degree, the question of title is academic due to Mr. Adelson's tight control over the company. Still, investors and analysts have said they are eager for answers regarding the company's plans for its leadership following a strong run by Mr. Adelson, who built Las Vegas Sands into a powerhouse by moving more quickly than his rivals to cash in on the gambling boom in Asia.

Two former executives who had been seen by people inside the company as potential successors to Mr. Adelson left Sands under acrimonious circumstances. Bill Weidner, a former president and chief operating officer at Sands, left the casino operator in March 2009 after almost 14 years. He had said he disagreed with Mr. Adelson over what course to take after the company's debt piled up and its shares plunged during the financial crisis.

Sands fired a previous Macau chief executive, Steve Jacobs, in July 2010. The former executive's subsequent wrongful termination lawsuit spawned U.S. bribery investigations into Sands' operations, the company has said. Sands has denied the claims in Mr. Jacobs' continuing suit and said it is cooperating with federal investigators.

Mr. Adelson has sued Wall Street Journal reporter Kate O'Keeffe for libel. A spokeswoman for the Journal, which wasn't named in the suit, has said the newspaper will "vigorously defend" Ms. O'Keeffe.

Chester Yung contributed to this article.

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