A day after the Tokyo Stock Exchange launched its new high-speed trading system, meant to capture the new need-for-speed in financial markets, U.S. exchanges were quick to tout how swift their systems are.

New York Stock Exchange parent NYSE Euronext said on Tuesday its all-electronic Arca venue executes buy and sell orders in as little as 650 microseconds, round-trip, now that it is connected to the company's new universal trading system.

NYSE Euronext's slower Big Board processes trades in less than five milliseconds, a spokesman said, about on par with Tokyo's new Arrowhead system.

NYSE Euronext is among the world's fastest exchange operators. However, it is probably not the leader in a race that is more competitive than ever and it is difficult to measure and compare venues because there is no globally accepted standard.

Speed is a key concern for all investors, particularly the so-called high-frequency traders that use sophisticated algorithms to make thousands of trades per second and account for about 60 percent of all U.S. stock trading.

BATS Global Markets, a privately-owned exchange operator often lauded for its speedy trading infrastructure, said on Tuesday its U.S. platform recently reduced its average order latency from 400 microseconds to 250 microseconds.

BATS measures the time it takes to accept, process, and acknowledge or fill a member order, its website said.

A millisecond is a thousandth of a second; a microsecond is a millionth of second.

Nasdaq OMX emailed reporters late Monday noting its centerpiece Nasdaq Stock Market -- also seen as a top venue in terms of speed -- accepts, processes and acknowledges or fills orders in less than one millisecond and is capable of sub-250 microsecond average speeds ...

Analysts say speed, known as latency in trading industry parlance, is now more vital than ever as banks, funds and independent trading firms scramble to improve technology in order to get better prices, or fills, when they trade.

Tokyo's upgrade could accelerate competition among North American, European and Asian exchanges, and broaden horizons for investors, said Sang Lee, managing partner specializing in market structure at Boston-based consultancy Aite Group.

It could fundamentally change the way things are done in Asia, Lee said of the possibility that alternative venues could gain traction there. With latency coming down, people might be more open to trading in other locations.

Also on Tuesday, NYSE Euronext said it made changes to its global data feed to tap into Tokyo's Arrowhead platform.

(Reporting by Jonathan Spicer; editing by Andre Grenon)