As Wal-Mart Stores Inc. pushes into China, its reluctance to allow unions into its stores here is moving the company toward a potential showdown with the government and its biggest trade-union group...the All-China Federation of Trade Unions, or ACFTU...The company...says that it did not agree to unionize, but to abide by a Chinese law barring companies from obstructing workers from forming unions. Mike Duke, chief executive of Wal-Mart International, said early this month that as far as he knew, no Wal-Mart worker at any of its 58 stores in China had expressed an interest in forming a union. A company spokeswoman said subsequently that some workers may have discussed it, "but it takes more than scattered interest for the company to be required by law to respond."...ACFTU has said that if Wal-Mart does not acquiesce to trade-union wishes, it may start enforcing this little-used regulation on the retailer...French retailer Carrefour SA, Wal-Mart's biggest rival, is 70% unionized in China. McDonald's Corp., Motorola Inc. and other Western companies have allowed union organization in areas where workers request it.