Amid a growing clamour over the role of high-frequency traders in the markets, Virtu Financial has delayed the start of its pitch to investors on its initial public offering, according to people familiar with the matter.

The high-speed trading firm decided late Tuesday to move back the launch of the deal by at least a week, the people said. The New York-based company, which had initially expected to begin marketing the IPO by Friday, still intends to move forward with the offering.