NEW YORK, JUNE 18 -- The American Stock Exchange, Chicago Board Options Exchange and Cincinnati Stock Exchange announced plans today to start a computerized, nighttime trading market for stocks and stock options.

Like an after-hours trading plan announced last week by the New York Stock Exchange, the proposal aims to regain some of the business in U.S.-listed issues captured by foreign competitors -- especially the London and Tokyo exchanges -- while U.S. stock markets are closed.

"The global marketplace is here and there is no turning back the clock," said Amex Chairman James R. Jones. "Those that seize the opportunity now to provide investors with a market at any time will emerge as the major players in the securities industry of the future."

Exchange officials said their system could be operating in two to three years, although they said many details had yet to be worked out. The plan also must be approved by the Securities and Exchange Commission.

The new system would operate between 6 p.m. and 6 a.m. Eastern time. Stocks now trade from 9:30 a.m. to 4 p.m. and options from 9:30 a.m. until 4:10 or 4:15 p.m.

Reuters Holdings PLC would provide the computer networking that would tie into a main computer to be built and maintained by the Chicago Board Options Exchange.

The CBOE and the Amex would provide a market in their stock options, while the Cincinnati Exchange would provide trading in stocks listed on that regional exchange. Options are financial instruments that give holders the right to buy or sell a specific number of shares of a stock at a designated price for a certain amount of time. Options are traded for stocks listed on exchanges or traded over the counter.

The deal is a sign of cooperation at a time of movement toward greater competition among exchanges that handle stock options. A new federal rule allows for multiple listings of stock options, which now are assigned to particular exchanges.

Under the computerized nighttime system, the marketplace that establishes itself as the primary exchange for a particular issue will handle the stock option in the after-hours session.