Federal regulators Monday approved a New York Stock Exchange plan to trade stocks after the 4 p.m. closing bell in an important move toward round-the-clock trading in U.S. markets.

The Securities and Exchange Commission voted 4-1 for a two-year pilot program for after-hours trading sessions designed to make the NYSE more competitive in the global marketplace."Today's proposal is an important first step toward a 24-hour securities trading capability in the United States," SEC Chairman Richard Breeden said.

"At first blush the proposal before us today may seem incremental, but its effect will be felt around the world as a sign that the U.S. markets are changing their habits to meet the needs of an increasingly globalized marketplace," he said.

The sessions are the first of their kind in the NYSE's 199-year history and move the exchange even further into the electronic age. NYSE spokeswoman Sharon Gamsin said the exchange plans to begin after-hours trading June 13.

The after-hours plan comes as the NYSE, the nation's biggest stock exchange, gradually is losing market share to other domestic exchanges and to overseas markets. The sessions are designed to capture some of that lost business.

The plan represents a concession by the NYSE to the rise of computerized stock trading that bypasses its traditional auction-style trading system. The new sessions would not involve the middlemen known as "specialists" who regulate trading on the exchange floor.

The new trading, known as "crossing sessions," will extend the normal 9:30 a.m. to 4 p.m. market day by 75 minutes.

The first session would run from 4:15 p.m. until 5 p.m. and permit trading at the market's closing price. Orders placed by institutional and individual investors during that session would be matched up and executed at 5 p.m.

In it, orders to buy or sell shares of stock would be entered and paired off electronically. Trades that don't find a match would carry over to the next day. In addition, prearranged trades would be entered and executed during the session.

The other session, from 4 p.m. to 5:15 p.m., would allow traders to execute computerized program trades consisting of a basket of at least 15 stocks with a market value of $1 million.

The session is designed to attract certain forms of trading now being done in London. Users are likely to be institutions such as pension funds, mutual funds and investment houses.

SEC Commissioner Edward Fleischman voted against the plan, raising concerns that the program trading session did not require enough disclosure by traders.