Special counsel Robert Mueller has requested an interview with President Donald Trump in the ongoing Russia investigation.

It's unclear whether Trump will accept the request, but if he does, Mueller will have a lot to ask him.

Here is what Mueller would likely focus on in a potential interview.

Special counsel Robert Mueller is getting closer to his key witness in the Justice Department's Russia investigation: President Donald Trump.

While Trump has said he'd let Mueller question him under oath, his lawyers have advised him against agreeing to an interview, concerned that the president will lie or contradict himself, The New York Times reported on Monday.

Mueller, the former FBI director, is leading the probe into alleged collusion between the Trump campaign and Russia during the 2016 election, and whether Trump obstructed justice during the course of that probe.

Trump's lawyers worry that if he makes false statements during the interview, investigators could charge him with perjury, according to the Times.

A majority of respondents to a recent poll say they want Trump to agree to Mueller's request, but it's unclear what the president — and his lawyers — will ultimately decide.

After saying he was "100%" open to being interviewed, Trump later said it's "unlikely that you'd even have an interview" because there was "no collusion." Yet sources told CNN that Trump still wants to testify under oath because he has experience doing so in business lawsuits and thinks he can outsmart Mueller.

A sit-down with Trump would give Mueller the opportunity to ask the president about a wide-range of issues related to the Russia investigation.

Here's what Mueller would likely focus on: