Santa Fe Southern Pacific Corp. said it had postponed an initial public offering of stock for up to 20% of its oil and gas operations because of the stock market's recent volatility . . . Japan has prohibited Tomei Trading Co. from making any exports for one month as a punishment for illegal sales of computers and integrated circuits to China, the Ministry of International Trade and Industry reported . . . Legislators from Mexico and Canada said they may negotiate a new trade agreement similar to the one Mexico just signed with the United States.