WASHINGTON (AP) — The Securities and Exchange Commission is embarking on a broad plan to tackle growing concerns about the impact of high-speed computer-based trading on equity markets.

In a speech Thursday, SEC Chair Mary Jo White outlined new rules and regulations that aim to boost market stability and fairness, enhance transparency and improve markets for smaller companies.

White's proposals come amid mounting debate about the impact of superfast computers and algorithms, which now account for a majority of trading volume. The increasingly complex electronics systems that run stock trading have come under strain in recent years. They have resulted in incidents like the 2010 "flash crash," when a computer problem sent stocks down wildly.

The proposals will be refined by SEC staff in coming months before being considered by the full commission.