London (CNN Business) 1. Trump and the Fed: Does President Donald Trump have the legal authority to fire Federal Reserve Chairman Jerome Powell? US markets could be volatile during a shortened session Monday following reports that Trump has been consulting his advisers about just that question.

The US Treasury Department is already in damage control mode. Treasury Secretary Steven Mnuchin spent Sunday on the phone speaking with the chief executives of six of the country's largest banks in an effort to avoid another round of market whiplash.

The CEOs of JPMorgan Chase ( JPM ), Wells Fargo ( WFC ), Goldman Sachs ( GS ), Morgan Stanley ( MS ), Bank of America ( BAC ) and Citi ( C ) each said they have "ample liquidity" to lend to consumers, businesses and perform other market operations, Treasury said in a statement Sunday evening.

Wall Street had a rough end to a brutal week on Friday, keeping it on track for its worst month since the financial crisis in 2008, and the phone calls were part of an effort to get ahead of further market jitters. A decision by Trump to fire his Fed chairman would likely exacerbate recent market volatility.

It was the second time over the weekend that Trump's finance chief tried to send a reassuring message to investors. A day earlier, Mnuchin tweeted that he had spoken with the president, relaying a message from Trump: "I never suggested firing Chairman Jay Powell, nor do I believe I have the right to do so."

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