Wall Street stocks finished at new records on Monday, shrugging off worries about a US criminal probe of the Federal Reserve that initially weighed on equities.

Both the Dow and S&P 500 ended the day with modest gains of 0.2 percent, which was good enough to lift both indices to records for a second straight day.

The Nasdaq also bounced back from early losses after Sunday night's disclosure of the US Department of Justice probe into the Federal Reserve dented stocks in the early going, while lifting gold and silver prices to new all-time highs.

Fed Chair Jerome Powell confirmed the "unprecedented" subpoenas against the bank in a rare video address, which he blasted as part of US President Donald Trump's pressure campaign for aggressive interest rate cuts.

Powell said in his statement that "the threat of criminal charges is a consequence of the Federal Reserve setting interest rates based on our best assessment of what will serve the public, rather than following the preferences of the president."

But there was extensive pushback against Trump, not only in a forceful statement jointly signed by three former Fed chiefs, but on Capitol Hill, where at least two Republican senators baulked at moves to undermine central bank independence.

"The market doesn't really believe it's going to come to a prosecution," said Briefing.com analyst Patrick O'Hare. "It's a lot of bluster."

O'Hare said Monday's gains reflect investors' inclination to "keep calm and buy the trend," which has been pointing higher.

The dollar fell against the euro and the pound, as did the price of the benchmark 10-year US Treasury bond, sending its yield slightly higher.

Gold climbed above US$4,600 an ounce while silver approached US$86 an ounce as investors sought traditional safe havens.

"Beyond monetary and political concerns, gold remains well supported by ongoing geopolitical risks," said Forex.com analyst Fawad Razaqzada.

Trump said on Sunday that he was considering military action against Iran following reports of hundreds of deaths during a violent crackdown on the protesters.

"We're looking at it very seriously," Trump told reporters on Air Force One. "The military is looking at it, and we're looking at some very strong options."

Oil prices edged higher in volatile trading on Monday as protests in Iran and the US seizure of Venezuela's crude supplies stoking geopolitical risks.

Banking stocks meanwhile took a hit from Trump's call to cap credit card costs at 10 percent, a change that would make credit less available and hurt consumers and businesses.

American Express, JPMorgan Chase and Visa were among the biggest losers on Wall Street's blue-chip Dow index.

The S&P 500 rose 0.2 percent, to 6,977, the Dow also rose 0.2 percent, to 49,590, while the Nasdaq rose 0.3 percent, to 23,733. (AFP)