The Federal Reserve wants U.S. banks to set aside more money to cushion against unexpected losses, a key step in preventing another financial crisis.

The Fed on Thursday proposed rules requiring the nation's largest banks hold at least 6 percent of their assets in capital reserves. That's up from a minimum of 4 percent currently required and in line with international standards.

The 2010 financial overhaul mandated regulators raise capital requirements for banks.

The banks have lobbied vigorously against the proposals. They say setting aside so much money in reserve could limit what they could lend.

The rules are open to comment until September. They will be finalized after that.

(Copyright 2012 by The Associated Press. All Rights Reserved.)