The United Steelworkers agreed to a second 24-hour extension of its contract with USX Corp., postponing for a second straight day the possibility of a strike at the nation's largest steelmaker.

Rupert Murdoch, overcoming a cash crunch that had threatened his media empire, said he had persuaded bankers to reschedule $7.6 billion in debt owed by his News Corp.

A federal judge ruled that the government violated banking laws in its 1988 seizure of 12 of 20 Texas-based MCorp banks, the second such ruling to go against federal banking regulators. Lawyers for MCorp, which is now in bankruptcy, sought the return of the banks or $70 million in compensation for their creditors and shareholders, but U.S. District Court Judge Robert W. Porter did not rule on a remedy yesterday.

General Dynamics plans to lay off about 1,200 workers this year at its tank-making plants in Michigan, Ohio and Pennsylvania. It will be the second round of layoffs in less than a month for the nation's second-biggest defense contractor.

Mortgage rates were mixed this week. Fixed-rate mortgages averaged 9.56 percent, down from 9.61 percent last week, while one-year adjustable-rate mortgages had an average initial rate of 7.75 percent, up from 7.69 percent last week, the Federal Home Loan Mortgage Corp. said.

United Press International is being considered for possible purchase by a Thai publisher and a group of Hong Kong industrialists.

IBM said a team led by its federal sector division in Manassas was awarded a five-year, $25 million contract to provide a nationwide data communications network for the federal court system.

NV Philips said its only prototype of an advanced compact disc player that can record as well as play was stolen from a development center in the Netherlands and sold in a neighborhood bar for $90. A shopkeeper returned the player to Philips, but the theft hasn't been solved.

Aerospace companies General Dynamics, McDonnell Douglas, Rockwell International and Space Propulsion & System received a $502.6 million Air Force contract for development of the national aerospace plane.

Westinghouse received contracts worth $103 million for Navy submarine propulsion units and Air Force support in Saudi Arabia.

Federal Express will close three plants in Britain, affecting 1,850 workers and costing the firm $114 million. It plans to revamp British operations, concentrating on high-priority next-day and second-day domestic and international services.