US regulators are asking big banks to provide investors with more-detailed disclosures about their trading businesses, a push that could peel back the curtain on a huge and volatile source of Wall Street revenues, according to people familiar with the matter.

Communications between Securities and Exchange Commission officials and executives from some of the largest US banks have been informal and preliminary, the people said. But the SEC may send comment letters to the biggest trading firms - JP Morgan Chase, Bank of America, Citigroup, Goldman Sachs and Morgan Stanley in the coming months, asking them to give investors more details in the future, some of the people said.