"These Chinese-owned apps are increasingly being used to censor content and silence open discussion on topics deemed sensitive by the Chinese Government and Communist Party," Rubio wrote in his letter to Mnuchin. "There continues to be ample and growing evidence that TikTok's platform for Western markets, including the U.S., is censoring content that is not in line with the Chinese Government and Communist Party directives."

Rubio announced his plans in a tweet on Wednesday, and letter sent a letter to Treasury Secretary Steven Mnuchin requesting the Committee on Foreign Investment in the United States to look into "national security implications" of the deal.

Sen. Marco Rubio, R-Fla., will ask U.S. authorities to investigate the 2017 acquisition of Musical.ly by TikTok, accusing the China-based app of censorship.

In a tweet Tuesday, Rubio he said he also asked the Trump administration "to fully enforce anti-boycott laws that prohibit any U.S. person — including U.S. subsidiaries of Chinese companies from complying with foreign boycotts seeking to coerce U.S. companies to conform with #China's government views."

In a statement, a TikTok spokesperson said: "TikTok US is localized, adheres to US laws, and stores all US user data in the US. Our content and moderation policies are led by our US-based team and are not influenced by any foreign government. The Chinese government does not request that TikTok censor content, and would not have jurisdiction regardless, as TikTok does not operate there."

The letter comes as the relationship between China and U.S. corporations is under a microscope. The National Basketball Association became embroiled in an international dispute after the general manager of the Houston Rockets, Daryl Morey, tweeted a message in support of anti-government protests in Hong Kong over the weekend. While the NBA initially released a statement saying it had "great respect for the history and culture of China," Commissioner Adam Silver later said the NBA is not in the place to "adjudicate" between different viewpoints.

As of Wednesday, 11 of 13 Chinese businesses listed as official partners on the NBA China website have distanced themselves from the NBA, CNBC reported.

TikTok has quickly become one of the most popular social media apps worldwide, especially among Gen Z users. The app, owned by the Chinese company ByteDance, features user-generated videos set to a variety of songs accessible through the app. Unlike other popular social media apps like Facebook-owned Instagram, TikTok's feed of videos is not based on users following specific accounts, but rather relies more heavily on its algorithm to learn user interests.

The app was molded from ByteDance's 2017 acquisition of Musical.ly, a lip-syncing app developed in China that also had a large following in the U.S. At the time, TechCrunch reported that the deal was worth up to $1 billion. ByteDance ultimately folded Musical.ly's brand into TikTok to reflect its wider range of content.

TikTok is not the only Chinese app that has gained traction among U.S. users. Apps developed by Chinese companies or those with large Chinese investors brought in revenues of $674.8 million in the U.S. in the first quarter of 2019, according to data previously compiled by Sensor Tower for CNBC. "PUBG Mobile" and "Clash of Clans," two games made respectively by Chinese company Tencent and one of its subsdiaries, have also gained a large U.S. following.

TikTok recently announced it would not allow paid political ads on its platform, saying it did not fit into its overall experience. A U.S. investigation would add to government scrutiny from the U.K. which launched an investigation into whether TIkTok violated Europe's General Data Protection Regulation.

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