The Nasdaq stock market was yesterday poised to complete the purchase of the Instinet electronic marketplace and brokerage unit of Reuters for about $1.8bn, according to people familiar with the matter.

The deal, which could be announced today, would see the second-largest US stock market become a bigger threat to the New York Stock Exchange by buying back order flow it lost in the late 1990s with the rise of electronic communications networks (ECNs) such as the Inet unit of Instinet.