WASHINGTON, Sept 25 (Reuters) - FBI Director Christopher Wray faced criticism from the White House for the second time in a week on Friday when President Donald Trump's chief of staff questioned his ability to detect voter fraud as the November election draws near.

Wray told lawmakers on Thursday he has not seen evidence of a "coordinated national voter fraud effort," undercutting the Republican president's unfounded assault on mail-in balloting before his Nov. 3 contest against Democrat Joe Biden.

Mark Meadows, the White House chief of staff, denigrated Wray during an interview with CBS "This Morning."

"With all due respect to Director Wray, he has a hard time finding emails in his own FBI, let alone figuring out whether there's any kind of voter fraud," he said without elaborating.

A top federal prosecutor in the battleground state of Pennsylvania on Thursday said his office and the FBI were investigating whether nine military ballots cast for Trump had been handled improperly.

Meadows suggested to CBS that Wray "drill down on the investigation that just started ... Perhaps he needs to get involved on the ground and then he would change his testimony on Capitol Hill."

The FBI had no comment on Meadows' remarks.

Trump appointed Wray as FBI director after he fired James Comey in 2017 during a federal probe into ties between the 2016 Trump presidential campaign and Russia.

Last week, Wray testified before a House of Representatives committee that his biggest concern in the 2020 election was the "steady drumbeat of misinformation" coming from Russian interference.

That prompted Trump to retort, "I did not like his answers yesterday."

Wray's statements run contrary to the Republican president's stances as he seeks re-election on Nov. 3 in the race against Democrat Joe Biden. Trump continues to downplay the threat from Moscow and argues that mail-in voting, which many states are relying on during the coronavirus pandemic, poses a threat to election security.

Asked if Trump had confidence in Wray, Meadows told reporters on Friday he has not spoken to the president about it.

Trump himself has repeatedly and without evidence questioned the increased use of mail-in ballots, an established method of voting in the United States.

He also continues to bristle at U.S. intelligence agencies' finding that Russia acted to boost Trump's 2016 presidential campaign and undermine his Democratic rival, Hillary Clinton.