WASHINGTON — An independent federal watchdog has opened more than three dozen investigations into the Trump administration to determine if it has illegally withheld billions of dollars in congressionally approved funds, raising the odds of a high-stakes constitutional clash over the power of the government’s purse.

The acknowledgment by the Government Accountability Office came Tuesday, as House and Senate Democrats estimated for the first time that President Donald Trump might have blocked the delivery of at least $430 billion during his first 100 days in office. That imperiled money enacted for foreign aid, green energy, health and transportation-related programs, potentially in violation of the law.

The dispute originates in Trump’s vast, chaotic and continued reconfiguration of the federal government. Since the first days of Trump’s term, he and his top advisers — including tech billionaire Elon Musk — have shuttered programs while blocking or slowing a wide array of funds seen as wasteful, unnecessary or incompatible with the president’s broader political agenda.

Many Democrats and legal scholars contend that Trump’s budget maneuvers violate the Constitution, which vest the powers to tax and spend with Congress, not the executive branch. The spending interruptions have also prompted a wave of court challenges as state officials, nonprofits and other federal aid recipients say the White House has acted illegally.

On Tuesday, Gene L. Dodaro, comptroller general of the Government Accountability Office, revealed at a congressional hearing that his office had opened “39 different investigations” into the administration. He suggested some of the focus was on cuts or changes to spending at the Education Department, the Environmental Protection Agency and other major federal offices.

Under a 1970s law, the Government Accountability Office has the power to investigate whether an administration has improperly withheld authorized funding in defiance of Congress. The watchdog has the power to sue if it finds the administration illegally impounds funds.

Dodaro did not signal how his office might proceed.

He told lawmakers that some federal agencies had not been “responsive” to his requests for information, while the White House’s budget office had largely ignored his entreaties.

“We’re trying to get information from the agencies about what their legal position is for not expending the money,” Dodaro said.

He acknowledged the inquiries after questioning from Sen. Patty Murray, D-Wash., who leads her party on the chamber’s top appropriations panel. Earlier Tuesday, Murray and her counterpart in the House, Rep. Rosa DeLauro, D-Conn., issued the estimate that more than $400 billion in congressionally appropriated funds had been slowed or blocked under Trump.

At the hearing, Murray faulted Trump for having “unilaterally frozen” funds in ways that “wreaked havoc for our families and communities across the country.”

A spokesperson for the White House budget office did not immediately comment. The Government Accountability Office declined to comment further.