The US attorney general has allowed prosecutors to investigate alleged irregularities in the presidential election, prompting a senior justice department official to quit.
William Barr said inquiries could only be into “apparently-credible” claims. Such investigations are normally the remit of individual states, but Mr Barr said this was not a hard and fast rule.
Donald Trump refuses to accept Joe Biden’s projected victory, and has made unsubstantiated fraud claims. The president’s campaign is seeking an emergency injunction in Pennsylvania to prevent Mr Biden’s victory being certified in the state.
The president-elect’s projected win there on Saturday took him over the threshold of 270 electoral college votes needed to secure victory nationwide.
Mr Trump’s spokeswoman vowed the legal battle to contest Mr Biden’s victory was only just beginning. “This election is not over,” White House press secretary Kayleigh McEnany told a news conference. “Far from it.”