Sen. Elizabeth Warren, D-Mass., is calling on the Securities and Exchange Commission to delay the highly anticipated initial public offering of SpaceX, arguing that the company's unprecedented size, governance structure, and valuation raise significant concerns for investors and financial markets, CNBC reported Wednesday.

In a 12-page letter sent to the SEC, Warren urged regulators to postpone the effectiveness of SpaceX's registration statement, warning that the planned offering could pose what she described as "unprecedented threats to investor protection and market integrity."

"Given the unprecedented threats to investor protection and market integrity posed by the biggest IPO in history, you must delay any eventual acceleration of the registration statement's effectiveness accordingly," Warren wrote.

The senator raised concerns about SpaceX's reported acquisition of xAI, the artificial intelligence company owned by billionaire entrepreneur Elon Musk. Warren said regulators should closely examine whether the transaction could result in inaccurate valuations or accounting disclosures that could mislead investors.

She also questioned Musk's influence over the company, arguing that his position as majority shareholder creates potential conflicts of interest and leaves investors vulnerable to governance risks, CNBC reported.

Warren further warned that the company's anticipated inclusion in major stock market indexes could expose millions of Americans to risks they did not actively choose to take.

"For investors who pick and choose their specific investments, they at least are able to avoid investing in companies that engage in risky or unfair practices," Warren wrote. "But the SpaceX IPO creates a new concern: that major stock market indexes are being rigged in a way that would force millions of investors in passive index funds ... to invest in SpaceX and face exposure to SpaceX's significant risks with no choice in the matter."

The letter arrives just days before SpaceX is scheduled to begin trading Friday in what is expected to be the largest IPO ever conducted in U.S. markets.

The aerospace company is reportedly seeking to raise a record amount of capital at a historic valuation. In an unusual departure from standard IPO practices, SpaceX has set a fixed offering price of $135 per share rather than establishing a price range that can be adjusted based on investor demand during the roadshow process.

The company is also expected to reserve approximately 30% of the offering for retail investors, a substantially larger allocation than is typical for major public offerings. Reports indicate the retail portion alone could total some $22.5 billion.

Supporters of the IPO have argued that the large retail allocation will give ordinary investors a rare opportunity to participate in a company that has remained private throughout much of its explosive growth.

Critics, however, contend that the structure could expose individual investors to heightened risks if the stock experiences significant volatility after trading begins.