WASHINGTON (NEXSTAR) — Lawmakers on both sides of the aisle are skeptical of Facebook’s plan to launch its own cryptocurrency, and they weren’t shy about letting the social media giant’s CEO know it.

Mark Zuckerberg underwent another grilling on Capitol Hill Wednesday as he tried to sell the idea.

“There are more than a billion people around the world who don’t have access to bank account but could through mobile phones,” he said, explaining why he thinks the currency dubbed Libra is needed.

His pitch fell flat.

“You’ve lost these stable partners, I would say, and I find it highly concerning,” Rep. Ann Wagner, R-Mo., said, referring to the banking partners who left the project citing security concerns. “PayPal, Visa, Mastercard, Stripe… Why do you think they dropped out?”

“I think because it’s a risky project, like you said,” Zuckerberg replied.

He promised Facebook won’t launch the project until it’s approved by banking regulators. Treasury Secretary Steven Mnuchin said he’s not ready to do that.

“The launch is premature,” he testified. “They had not addressed fundamental issues around money laundering.”

Rep. Emanuel Cleaver, D-Mo., said he met with Zuckerberg privately before the hearing. He’s still got security concerns.

“When we’re talking about moving invisible money from country to country, I think that is a really, really big deal,” Cleaver said. “I think that we’re going to have to have some federal involvement.”

Rep. Bill Huizenga, R-Mich., agrees there are a lot of unanswered questions.

“The jury is out as to whether a Facebook-based currency is good for society,” he said.

Zuckerberg said he’s committed to resolving lawmakers’ concerns.