Datek Online Holdings Inc. said Tuesday it would let its clients trade stocks before the market opens, becoming the first online broker to offer the service amid growing investor demand to trade around the clock.

Datek, the No. 4 U.S. online broker that was the first to offer trading after the market closed this summer, also said it was extending its after-hours session to 8 p.m. EDT (0000 GMT) from 5:15 p.m. EDT (2115 GMT).

"(This) will create the first 12-hour trading day for individual investors," it said in a statement.

Privately-held Datek of Iselin, N.J., said its clients would be able to start placing limit orders for Nasdaq stocks at 8:00 a.m. EDT (1200 GMT) on Wednesday, 90 minutes before the market opens at 9:30 a.m. (1230 GMT).

Their orders would go through Island ECN, the No. 2 U.S. electronic communications network (ECN) that matches stock orders and has Datek as its majority shareholder, it said.

Datek's announcement comes a day after Island said it would extend its operating hours by nearly three hours to have it begin at 8 a.m. EDT (1200 GMT) and end at 8 p.m. (0000 GMT).

Regular market hours at such traditional exchanges as the New York Stock Exchange end at 4:00 p.m. EDT (2000 GMT). But the Big Board as well as the Nasdaq market have announced plans to extend those hours in an apparent effort to fend off competition from ECNs, which include Archipelago.

Rival brokers have been quick to follow Datek's example. On Aug. 25, Discover Brokerage of Morgan Stanley Dean Witter & Co. and Dreyfus Brokerage Services of Mellon Bank Corp. were the latest to offer after-hours trading, allowing investors to trade in the 200 most widely traded U.S. stocks.

John Mullin, president of online brokerage services at Datek, said the broker would likely benefit from the fact that trading was usually heaviest during morning hours.

"There are a lot of dealers that jockey and try to understand where everybody else is (positioned in the market)," he told Reuters.

About 20 percent of Datek's daily trades often occur between 9:30 a.m. and 10:15 a.m., according to the statement.

Meanwhile, nearly 2 percent of trades occur between 4:00 p.m. and 5:15 p.m., it said, adding that the amount nevertheless accounted for about a third of the 3,000 trades executed by Island.

Datek has 285,000 funded accounts and executes an average 60,000 trades per day, according to a spokesman.

Mullin said Datek would eventually let investors deal in Big Board stocks before and after market hours.

He also said it was rolling out a check writing service and planning to introduce debit and credit cards.