The Justice Department is expected to tell WorldCom Inc. and Sprint Corp. whether it will sue to block the companies' $146-billion merger, according to people familiar with the situation. Justice Department staff lawyers have recommended a court challenge because of concerns about No. 2 U.S. long-distance company WorldCom combining with No. 3 Sprint. The companies have discussed a proposal to sell Sprint's long-distance telephone and Internet backbone assets to meet U.S. and EU competition concerns, according to people familiar with the transaction. Bernard Ebbers, president of WorldCom, is likely to walk away from the deal rather than wage a legal fight if the Justice Department challenges the merger, people familiar with the situation said. Meanwhile, Mario Monti, the European Commission's top antitrust official, visiting Washington this week, said he believes the merger should be blocked unless the companies propose "exceptional" remedies to allay concerns that the combination would reduce competition. WorldCom shares fell 25 cents to close at $37.50 on Nasdaq and Sprint fell 25 cents to close at $59.56 on the NYSE.