[SEC Halts Approval of High-Leverage ETFs, Citing Risk Concerns] The U.S. Securities and Exchange Commission (SEC) has issued a series of warning letters to some of the country's most prolific high-leverage exchange-traded fund providers, effectively blocking the launch of products designed to deliver two or three times the daily returns of stocks or commodities. In nine nearly identical letters released on Tuesday, the SEC informed companies including Direxion, ProShares, and Tidal that it would not proceed with reviewing proposed product offerings until key issues are resolved. The regulator's primary concern is that the risk exposure of these funds may exceed the SEC's limits on the level of risk funds can take relative to their assets. The letters direct fund managers to either revise their investment strategies or formally withdraw their applications.