By Jonathan Spicer

NEW YORK, Feb 9 (Reuters) – The heads of the top U.S. stock exchanges have poured cold water on the Obama administration’s plan to bar banks from proprietary trading.

The chief executive of NYSE Euronext said on Tuesday the president’s plan falls short of targeting what caused the financial crisis, while his counterpart at Nasdaq OMX group Inc, the day before, said the plan would probably have to be changed.

Obama last month surprised Wall Street with the ambitious proposal to limit risky trading by banks. Dubbed the ‘Volcker rule’ after Paul Volcker, the White House economics adviser, it would bar banks from proprietary trading, or placing bets on markets with their own money.

The proposal jolted markets. The shares of the New York Stock Exchange parent fell 3.8 percent, while those of the Nasdaq Stock Market parent tumbled 4.8 percent, on concerns the Volcker rule would reduce liquidity and trading volumes.

On a conference call with analysts and media, Niederauer said it would prove difficult to separate “the small fraction of equity volume that these banks do for their own account.