"Director Pompeo's statement sought not only to threaten Mr. Assange and WikiLeaks, but to definitively subvert the First Amendment and fundamental notions that are intrinsic to American democracy," the statement said.
The statement went on to compare Pompeo's "attempts to demonize" Assange as on par with Syrian President Bashar al-Assad.
Earlier in the week, Pompeo gave a speech railing against WikiLeaks as a "hostile intelligence service."
Pompeo's appearance at the Center for Strategic and International Studies, among his first forays into the public eye since being confirmed CIA director, came several months after WikiLeaks' publishing stolen emails from Hillary Clinton's campaign chairman John Podesta as well as the Democratic National Committee and just over a month since WikiLeaks published
a trove of files it said were from the CIA.
The CIA has neither confirmed nor denied their veracity.
In his Thursday speech, Pompeo accused WikiLeaks, Assange and Edward Snowden, a former contractor who leaked NSA documents to journalists, of disseminating classified information to "make a name for themselves."
Pompeo has in the past called for
Snowden to receive the death penalty.
He said people at the CIA found praise for WikiLeaks "both perplexing and deeply troubling."
"As long as they make a splash, they care nothing about the lives they put at risk or the damage they cause to national security," Pompeo said. "It's time to call out WikiLeaks for what it really is: a non-state hostile intelligence service often abetted by state actors, like Russia."
During the question and answer portion of the event, Pompeo said because Assange was not a US citizen and lived in the Ecuadorian embassy in London, he "has no First Amendment freedoms."
Although WikiLeaks describes itself as a media organization exposing powerful governments and companies, Pompeo said he viewed this as false.
"These are not reporters doing good work," Pompeo said. "These are people who are actively recruiting agents."
Pompeo said past administrations had been "squeamish" about going after people who published secrets he considered harmful to the US.
During the campaign rally in October, Trump said he loved WikiLeaks and regularly touted their disclosures. For a time before taking office, Trump did not endorse a report from the US intelligence community accusing Russia of being behind the hacks and using WikiLeaks to disseminate them in order to hurt the Clinton campaign.
Russia has denied any wrongdoing, and Assange has said WikiLeaks' source was not Russia.
WikiLeaks responded to Pompeo's comments in part by referencing a now deleted tweet he sent during the campaign referencing WikiLeaks' DNC trove.
Iran and North Korea
Until Trump tapped him to lead the CIA, Pompeo was a Republican member of Congress from Kansas. He was an outspoken critic of the Obama administration and the US nuclear agreement with Iran, officially known as the Joint Comprehensive Plan of Action or JCPOA.
As CIA director speaking at CSIS on Thursday, he was considerably less outspoken about his issues with the Iran deal, but did say Iranians were "on the march" and cited missile launches, their support of the Houthis in Yemen and military involvement in Iraq in the past two years.
"The list of Iranian transgressions has increased dramatically since the date that the JCPOA was signed," Pompeo said.
Pompeo said he viewed working with both European and Middle Eastern allies as integral to countering Iran, but also said the US' recent cruise missile strike on Syria likely sent a message of US strength to Iran.
"What I mean by that is, this was a decision-making process that was decisive, thoughtful and truly based on a factual understanding of the geopolitical importance of the things that are facing our nation today."
He went on to say the Iranians "ought to take note of the fact that this administration" is willing to take different measures than past administrations.
Pompeo also spoke about nuclear proliferation in North Korea and the potential of another nuclear weapons test in the coming days.
"Multiple administrations have tried to deal with the threat of an intercontinental ballistic missile capable of putting a nuclear warhead into the United States, and we're simply closer now than we have ever been at any time in North Korea's history," he said. "As the knowledge base increases and the capacity to deliver that increases and draws closer, it both reduces the option set to prevent it and makes more likely that you get a bad decision on a tough day from the leader of North Korea."
Like Trump, Pompeo said China was of utmost importance to solving the issue.
Asked if there was hope China could turn back or end the North Korean nuclear weapons program, Pompeo said, "I'm counting on it."