US regulators are preparing to tighten rules for large banks, which could raise their capital requirements by 20% on average, the Wall Street Journal reported on Monday (June 5), to boost the financial system's resilience after a spate of midsize bank failures this year.

Regulators are on track to propose the changes as early as this month, the WSJ reported, citing people familiar with the matter.

Last month, the US Federal Reserve's top regulatory official told Congress that the central bank would likely unveil its plan to ratchet up capital rules for banks this summer and ensure supervisors more aggressively police lenders following the bank failures.

Fed vice chair for Supervision Michael Barr said the central bank was "carefully considering" rule changes for larger regional banks.

The WSJ said that the precise amount of capital requirements will depend on the bank's business, with US megabanks with big trading businesses expected to face the largest increases.

Banks such as Morgan Stanley and credit card giant American Express that are heavily dependent on fee income, such as from investment banking or wealth management, could also face large capital increases, the WSJ said.

Morgan Stanley and American Express did not immediately respond to Reuters' request for comment.

  - Reuters