US exchanges have complained that the length of time taken by the Securities and Exchange Commission to review rule changes is hampering their ability to compete with overseas venues.

In Senate hearings last week on cross-border exchange mergers, Adena Friedman, executive vice-president, global strategy and data products at Nasdaq, said: "When we announce a proprietary initiative through a rule filing, our competitors react around the world. Often their response to our initiative is rolled out before we receive regulatory approval."