WATCH: Ted Cruz GRILLS Zuckerberg over Facebook's anti-conservative bias

On Tuesday, Facebook CEO Mark Zuckerberg testified before a joint session of the Senate Judiciary and Commerce Committees. When it was Sen. Ted Cruz's turn to ask questions, the Texas Republican grilled Zuckerberg on Facebook's bias against conservatives.

"Does Facebook consider itself to be a neutral public forum?" Cruz asked.

Zuckerberg claimed that Facebook's goal was not to engage in political speech, but noted that Facebook does police certain content it defines as hate speech or "anything that makes people feel unsafe in the community."

"Mr. Zuckerberg, I will say there are a great many Americans who I think are deeply concerned that Facebook and other tech companies are engaged in a pervasive pattern of bias and political censorship," Cruz said. He cited reports that Facebook had "routinely suppressed conservative stories from trending news." He also noted Facebook has blocked or suppressed conservative-leaning Facebook pages for violating community standards, most recently the page of Trump supporters Diamond and Silk.

Zuckerberg admitted that Silicon Valley is "an extremely left-leaning place" and said that he was working to ensure that Facebook remains unbiased.

Cruz followed up by asking if the Facebook CEO was aware of any posts by Democrats or Planned Parenthood that were taken down for violating Facebook's standards.

"I'm not specifically aware ... I'm not sure," Zuckerberg said in response.