WASHINGTON, March 10 — Two US Senate Democrats said they will propose today placing new limits on proprietary trading by banks and nonbank financial firms, widening the ‘Volcker rule’ backed by the White House.

Senators Jeff Merkley and Carl Levin said in a statement they will hold a news conference on legislation “to limit the types of high-risk bets, also known as proprietary trades, which contributed to the Wall Street collapse of 2008.”

The Volcker rule, named after White House adviser Paul Volcker, is aimed at limiting risky trading by banks.