Mike Pence may be in constant communication with Donald Trump, but when it comes to the billionaire's refusal to release his tax returns, the Indiana governor has one answer: "Talk to the campaign."

"I think I'd just recommend you talk to the campaign about timing on that," Pence told KTNV Las Vegas after a campaign stop this week in Henderson, Nev.

"I know he's under an audit at this time and given the — I think I saw a photograph of his tax returns, it was out about a year ago, and his tax returns are considerably longer than mine, than most Americans," Pence said of the Republican presidential nominee.

Trump's decision to stall the release of his tax documents, claiming that he will do so once they are no longer being audited by the IRS, has given Democrats ample material for their attacks. Hillary Clinton has capitalized on his refusal by suggesting the billionaire is likely hiding something about his personal fortune, how much he contributes to charity or whether he pays income taxes.

Her campaign released an ad on Thursday that showed Trump telling an Irish television station in 2014 that he would make his tax returns public if he ever ran for office. The ad later cuts to a more recent clip of him telling ABC's George Stephanopoulos his tax rate is "none of your business."

"As he works through that audit, then I know that they'll be making that available at the appropriate time," Pence told KTNV.

Trump, however, has not clarified what he intends to do if the IRS audit is not completed before the Nov. 8 election.