NEW YORK (Reuters) - The operator of the New York Stock Exchange said on Wednesday it will change the model of its NYSE MKT exchange to implement a so-called speed bump, in a direct challenge to the Investors’ Exchange, the newest U.S. stock exchange.

Traders work on the floor of the New York Stock Exchange (NYSE) shortly after the opening bell in New York, U.S., January 13, 2017. REUTERS/Lucas Jackson

NYSE Group, which is owned by Intercontinental Exchange Inc ICE.N (ICE), said it plans to change the name of NYSE MKT to the NYSE American, and to add a delay for incoming and outgoing orders and proprietary market data.

NYSE said NYSE American will have largely the same model as IEX Group’s Investors’ Exchange, including a 350 micro-second delay, except it will have electronic market makers with obligations to ease the trading of NYSE American-listed stocks.

IEX has said its speed bump was meant to even the playing field between fast traders and slow traders, while NYSE said its speed bump was to offer investors more choice.

“While we’re flattered by the imitation, investor protection is a philosophy, not a single product or order type,” said an IEX spokesman.

Unlike IEX, NYSE still has multiple trading venues, pays rebates to attract traders, allows trading firms to pay to locate their servers in the NYSE data center for faster access, and charges “excessive” data fees, he said.

The Investors' Exchange launched in August 2016 as the 13th U.S. stock exchange after a protracted approval process with regulators that included fierce resistance from incumbent exchanges including NYSE, Nasdaq Inc NDAQ.O and Bats Global Markets BATS.Z.

ICE Chief Executive Jeffrey Sprecher even called IEX “un-American” for trying to implement its speed bump, because it was unclear whether a stock market was allowed to delay stock orders.

NYSE American is a throwback to the American Stock Exchange, the exchange’s name before it was bought by NYSE in 2008. The exchange lists around 370 small companies and has a market share of less than 0.5 percent. IEX has a market share of around 2 percent.

New York-based IEX and its founders were thrust into the spotlight in March 2014 when they were featured in Michael Lewis’s book, “Flash Boys: A Wall Street Revolt,” which followed the group as it built what it saw as fairer, more simple market.

The book caused a heated debate on Wall Street after Lewis said the market was rigged by profit-hungry exchanges in favor of high-frequency trading firms.

This year IEX plans to start a listings business to compete against NYSE and Nasdaq.