ECONOMY The Treasury announced it will auction $4 billion in 44-day cash-management bills tomorrow to cover the short-term financing needs of the federal government.

COMPANIES Mack Trucks said its Mack Financial subsidiary won an extension of its revolving credit agreement to Aug. 8 and is talking with lenders about an extension to Dec. 31. Interco, the manufacturing firm that nearly destroyed itself by using junk bonds to fend off a takeover attempt by Steven and Michael Rales of Washington, apparently has solved its nagging debt woes by negotiating a restructuring agreement with its creditors. Trump Shuttle will launch regular air service between Boston and Atlantic City.

INTERNATIONAL The Mexican government plans to sell a 20.4 percent stake in the national telephone company by Dec. 20, the first stage in the country's largest privatization effort, newspapers reported. South Korea's current account balance posted a deficit of $1.58 billion in the first half of this year, down from a surplus of $2.56 billion in the same period last year.

REGULATION MCI's $1.25 billion acquisition of Telecom USA, an Atlanta-based long-distance telephone company, was approved by the FCC. CONTRACTS GE won $101 million in contracts for Navy shipboard weapons and for Air Force jet engine components. General Dynamics won a $63.8 million Navy contract for shipboard weapons systems. Contel Federal Systems of Chantilly won a $33.2 million Air Force contract for data processing systems. Arinc Research of Annapolis won a $9.9 million Air Force contract for satellite services.

EARNINGS USX said its second-quarter profit fell 15 percent, citing reduced steel earnings and a loss on the sale of Texas Oil & Gas Corp. assets. Wheeling-Pittsburgh Steel reported a 33 percent drop in earnings for the second quarter. Jaguar reported a pretax loss of $90.7 million in 1989, its worst financial performance for a decade. Xerox said its second-quarter earnings fell 27 percent because of declines in its insurance business.

PEOPLE Joseph R. O'Gorman Jr., who has held management posts with United and other airlines, was named USAir's executive vice president for operations. He succeeds Seth E. Schofield, who earlier became USAir president and chief operating officer.

ODD LOTS New York's five commodity exchanges halted trading four times, with the longest outage about 40 minutes, because of a data-transmission problem. A wire problem at AT&T's central office in Manhattan prevented data from being disseminated to customers off the trading floor. END NOTESProcter & Gamble sued a Kansas couple for allegedly spreading rumors that the company supports the ''Church of Satan.'' In a flier, the couple, James and Linda Newton, said the company's ''moon and stars'' trademark is a satanic symbol.