WASHINGTON (BLOOMBERG) - The White House pressured the US Attorney in Atlanta to quit because President Donald Trump was unhappy with a lack of cooperation from officials there on his unproven allegations of election fraud, the Wall Street Journal reported.

US Attorney Byung J. Pak, a Mr Trump appointee, was told to step down a day before the Jan 5 Georgia Senate run-off elections, the newspaper reported, citing people it didn't identify. The Republican incumbents lost both contests.

Earlier, the Washington Post reported that Mr Trump pressured Georgia's lead elections investigator to "find the fraud" in the state and become "a national hero" in a call made Dec 23.

Georgia Secretary of State Brad Raffensperger confirmed to the Post that Mr Trump placed the call, adding that he wasn't familiar with what the president specifically said.

The Post withheld the name of the investigator, who didn't respond to its requests for comment, because of the risk of threats and harassment directed at election officials.

In the case of Mr Pak, the federal prosecutor resigned abruptly in an email to colleagues that cited "unforeseen circumstances."

The reports follow a week after it was revealed that Mr Trump urged Georgia election officials in an hour-long call to "find" thousands of votes and recalculate the state's presidential election results to flip the state to him.

Georgia was one of five states won by Democrat Joe Biden in November that Mr Trump had won in 2016. The state had two recounts of the presidential vote, with each showing the same outcome: that Mr Biden had a narrow victory in a state last carried by a Democrat in 1992.

Dozens of rejected claims by Mr Trump and his associates that there had been widespread election fraud in the US, ranging from dead people voting to voting machines that changed Mr Trump votes to Mr Biden, have been thrown out of court.

Mr William Barr, the US Attorney-General who departed in December, also said that the Justice Department hadn't found such evidence.