(CNN) Chinese-owned social video app TikTok followed the lead of other, bigger social media companies Monday and turned down an invitation to testify in Congress, drawing scathing criticism from Republicans.
Missouri Republican Sen. Josh Hawley called TikTok's decision a "mistake," tweeting an invitation to the company to "come and testify tomorrow about your ties to Communist Chinese Party. I'll save a place for you."
The company, which has sparked a craze among American social media users, is growing to rival Instagram and Snapchat -- earning it increasing scrutiny by US officials who have raised privacy and security concerns about the app and its Beijing-based owner, ByteDance.
As policymakers grapple with the implications of TikTok's explosive rise, the company now finds itself caught in the middle of tensions between the United States and China.
That skepticism could have far-reaching consequences for TikTok, one of the few companies in recent years to challenge the dominance of tech giants including Facebook and Google. And it underscores how businesses with ties to China are increasingly facing disruption at a time of uneasy diplomacy between Washington and Beijing.
On Monday, TikTok said it wouldn't appear at a Tuesday hearing examining the tech industry's relationship to China after being called by the Senate Judiciary Committee's crime and terrorism panel.
"Unfortunately, on short notice we were unable to provide a witness who would be able to contribute to a substantive discussion," TikTok said in a statement. "We remain committed to working productively with Congress as it looks at how to secure the data of American users, protect their privacy, promote free expression, ensure competition and choice among internet platforms, and preserve US national security interests."
The hearing is being led by Hawley, a major tech critic who has fretted over what he has said is a willingness by tech companies to cooperate "with foreign adversaries ... leaving our data vulnerable to malevolent actors." Hawley's office said it will leave chairs open for TikTok and for Apple, which also declined to testify. The only company to testify at the hearing will be Microsoft, according to a list of witnesses released Monday by Hawley's staff.
Sen. Tom Cotton of Arkansas responded similarly. His office said in a statement: "TikTok's unwillingness to testify before Congress only underscores Senator Cotton's concerns that the company is beholden to the Chinese Communist Party and will not secure the rights and privacy of its American users."
The rising interest in TikTok's affairs reflect the platform's tremendous growth. The two-year-old app has been downloaded over 750 million times in the past year, according to the New York Times, citing figures from the app analytics firm Sensor Tower. That's tens of millions more downloads than for Facebook, Instagram, YouTube and Snapchat over the same period. And it reflects a 33% jump in downloads of TikTok compared to the year prior, Sensor Tower told CNN on Monday.
CFIUS's involvement follows requests by a number of US lawmakers for an investigation of TikTok in the wake of widespread democratic protests in Hong Kong.
Senate Minority Leader Chuck Schumer, Florida Republican Sen. Marco Rubio and Cotton have all questioned whether TikTok may have censored Hong Kong-related content on its platform — an allegation TikTok denies.
"TikTok, which has millions of active users across the U.S., is now ranked among the world's most downloaded apps," Rubio wrote last month to Treasury Secretary Steven Mnuchin. "There continues to be ample and growing evidence that TikTok's platform for Western markets, including those in the US, is censoring content that is not in line with the Chinese Government and Communist Party directives."
Last month, Schumer and Cotton wrote to Joseph Maguire, the acting director of national intelligence, asking the intelligence community to probe whether TikTok represents a risk to US security.
In that respect, TikTok finds itself in much the same position as another company with ties to China and that has become a political football: Huawei. Concerns about the security of Huawei's wireless equipment have led to numerous moves by US lawmakers and regulators to restrict the company's access to American markets. One major concern — which Huawei rejects — is the possibility that through its products, Americans' sensitive data could find its way into the hands of the Chinese government.
Schumer and Cotton made the connection explicit in their letter, saying that putting Huawei on a Commerce Department blacklist was an appropriate first step.
"However," they wrote, "further action is needed, particularly as China continues to shut out U.S.-based technology firms while promoting and expanding the global reach of its own companies. With over 110 million downloads in the U.S. alone, TikTok is a potential counterintelligence threat we cannot ignore."
TikTok has said it does not operate in China. Instead, TikTok's parent, ByteDance, offers a TikTok clone named Douyin for mainland Chinese users. TikTok's data on US users is stored in the United States, it claims, and that as a result, the data is not subject to Chinese law.
In a recent blog post, the company also pushed back against the censorship allegations.
"TikTok does not remove content based on sensitivities related to China," the company said. "We have never been asked by the Chinese government to remove any content and we would not do so if asked. Period."
National security experts offered mixed assessments on whether TikTok poses a true risk to US security.
Jason Healey, a former White House cybersecurity official under President George W. Bush, said lawmakers' attempt to invoke national security with regard to TikTok relies "on a stretched definition of national security and counterintelligence."
"Sure, TikTok can collect data and maybe send it to the PRC government, but mostly on teens," he said. "Yes, China will use it as propaganda and censor videos, but that's more about human rights than national security. Terrorists may use it for disseminating propaganda and to recruit, but is being threatening to China the right way to stop that?"
Peter W. Singer, a strategist at the New America Foundation and author of numerous books on technology in warfare, said TikTok's claims not to be influenced by any government, including the Chinese government, are unrealistic.
"For any company to say no government has influence over it is poppycock," he said. "To claim that of China is pure poppycock. Companies and their employees exist in a world where states have massive influence over their business and lives — through both formal mechanisms like laws and taxes, to informal ones, especially in authoritarian regimes, like threats of jail and worse."