China may inflict more damage on the U.S. through TikTok than it can accomplish through its military arsenal, according to the House Republican who has emerged as a leading voice on Capitol Hill on the growing challenge posed by Beijing.

Rep. Mike Gallagher, Wisconsin Republican and chairman of the House Select Committee on the Chinese Communist Party, told reporters on Monday that the committee’s investigations into Chinese information operations have made clear that TikTok, the short video-sharing site wildly popular with younger online browsers, poses a clear and present threat to the homeland.

TikTok and China-based parent company ByteDance remain under intense scrutiny in Washington. Lawmakers and regulators are reviewing ways to restrict the app over data privacy concerns and fear that the site could be used as a conduit for malign influence operations.

The Trump and Biden administrations have discussed banning or curbing TikTok’s presence in the U.S. but have met with commercial and philosophical pushback. Some say the move would amount to government censorship.

Still, Mr. Gallagher said, TikTok presents risks that Congress and the executive branch cannot ignore.

“If they could leverage that app in order to spread disinformation and poison Americans against America and American ideals, that would be more powerful than any conventional military weapon,” Mr. Gallagher said. “I’ve actually come to really focus on that in part because of what [Chinese President] Xi Jinping himself has said about the nature of ideological warfare, information warfare and even cyber” conflict.

Mr. Gallagher’s focus on information warfare is pivotal in TikTok’s tussle with the federal government. TikTok CEO Shou Zi Chew will head to Capitol Hill along with top executives from Meta, X and other social media sites on Wednesday for a Senate Judiciary Committee hearing about his app’s potential harm to children.

He was peppered with criticism on his last visit to Congress in March, but the grilling led to little substantive action to limit TikTok’s reach in the U.S.

Fears of the site’s seductive dangers are not limited to one side of the political aisle.

Rep. Raja Krishnamoorthi, Illinois Democrat, told reporters that the House China panel, set up after Republicans won control of the House in the 2022 midterm elections, is studying China’s propaganda techniques and tactics and believes TikTok and ByteDance present a unique, recurring problem.

“We keep learning that the platform, mainly through ByteDance and its control of TikTok, keeps amplifying content that’s beneficial to the [ruling Chinese Communist Party] and suppressing content that is critical of the CCP,” Mr. Krishnamoorthi said Monday.

Questions remain about whether Washington policymakers will act on alleged dangers from TikTok before the November elections. A bipartisan Senate bill taking direct aim at TikTok lost momentum last year.

Sen. Mark R. Warner, Virginia Democrat, said in October that he was worried about the future of the RESTRICT Act, which orders the Commerce Department to review technology offerings such as TikTok and determine their risks within 180 days.

The bill was introduced in March, and a majority of the Senate co-sponsored the legislation. That included 13 Republicans, 13 Democrats and Sen. Angus S. King, the Maine independent who caucuses with Democrats.

The bill has stalled, and the Biden administration has produced no significant proposals while reviewing national security concerns involving TikTok virtually since Mr. Biden took office in January 2021.

A Pew Research Center survey last month found that U.S. support overall for a TikTok ban had fallen from 50% in March to 38% by the end of the year. Among those 30 or younger, 71% either oppose or are unsure about the need to ban TikTok, with just 29% in support.

Montana last year became the first and only state to ban all TikTok use within its borders, but a judge put a preliminary injunction on the law before its Jan. 1 implementation date over concerns that it was unconstitutional. The state said it is appealing the ruling.

Commerce Secretary Gina Raimondo told senators in October that the issues involving TikTok are broad. She supported a bill that Senate Commerce Committee Chair Maria Cantwell, Washington state Democrat, was drafting to regulate the company.

Congressional action to potentially inhibit TikTok’s operations will likely become more difficult to pass as the November elections draw near.

Politicians facing contentious elections may wish to avoid discussion of banning TikTok until after the November contests. TikTok has more than 150 million monthly active users inside the U.S., according to TikTok’s website, and many of them are young Americans.

TikTok declined to answer questions Monday about the lawmakers’ assessments of threats from the platform.