Bill Gates isn't thrilled about the prospect of an Elizabeth Warren presidency.

While speaking at the New York Times Dealbook Conference on Wednesday, the Microsoft co-founder expressed concerns over the Massachusetts senator's signature wealth tax. Gates told reporter Andrew Ross Sorkin he was open to raising taxes and was willing to pay tens of billions of dollars; but he has his limits.

"I’ve paid over $10 billion in taxes, I've paid more than anyone in taxes," Gates said. "If I'd had to have paid $20 billion in taxes—fine. But when you say I should pay $100 billion? OK, I'm starting to do a little math about what I have left over."

Gates, the second richest man in the world, has a reported net worth of about $107 billion. Warren's proposal would apply a 6 percent tax on net worth above $1 billion and a 2 percent tax on those between $50 million and $1 billion. It's worth noting that Bernie Sanders' "Tax on Extreme Wealth" plan is much more aggressive than Warren's. The Vermont senator has proposed a 1 percent tax on net worth over $32 million for a married couple, with rates peaking at 8 percent on net worth over $10 billion.

Per Sanders' website:

The tax rate would increase to 2 percent on net worth from $50 to $250 million, 3 percent from $250 to $500 million, 4 percent from $500 million to $1 billion, 5 percent from $1 to $2.5 billion, 6 percent from $2.5 to $5 billion, 7 percent from $5 to $10 billion, and 8 percent on wealth over $10 billion. These brackets are halved for singles.

Under this plan, the wealth of billionaires would be cut in half over 15 years which would substantially break up the concentration of wealth and power of this small privileged class.

Gates went to say he has not spoken to Warren about her wealth tax proposal, and questioned whether she'd even be open to meet with him.

"I’m not sure how open minded she is—or that she’d even be willing to sit down with somebody who has large amounts of money," he said.

Warren took to Twitter on Wednesday night, insisting she was open to such a meeting.

Gates was then presented with a hypothetical question: Who would he back in a Warren vs. Donald Trump general election? His answer wasn't great.

"I’m not going to make political declarations," Gates said. "But I do think no matter what policy somebody has in mind … whoever I decide will have the more professional approach in the current situation, probably is the thing I will weigh the most. And I hope that the more professional candidate is an electable candidate."

He also reiterated his belief that Microsoft could've beaten Android in the mobile race, had it not been for the 2001 antitrust case.

"There’s no doubt that the antitrust lawsuit was bad for Microsoft, and we would have been more focused on creating the phone operating system and so instead of using Android today you would be using Windows Mobile," he said. "If it hadn’t been for the antitrust case ... we were so close, I was just too distracted. I screwed that up because of the distraction."

Another highlight was when Gates addressed his ties to Jeffrey Epstein, the convicted sexual predator who was found dead in his prison cell back in August. Gates said he had met with Epstein to discuss philanthropy, and secure donations to health initiatives. He says his efforts were unsuccessful. 

"I made a mistake in judgment that I thought that those discussions would lead, literally, to billions of dollars going to global health. It turned out that was a bad judgment. That was a mirage," Gates said. "And I gave him some benefit by the association. So I made a doubly wrong mistake there."

You can hear Gates' full statements in the video above.