The White House budget office has ordered a pause in grants, loans and other federal financial assistance, according to a memo sent to government agencies on Monday, potentially paralyzing a vast swath of programs and sowing confusion and alarm among the array of groups that depend on them.

The directive threatened to upend funds that course throughout the American economy: Hundreds of billions of dollars in grants to state, local and tribal governments. Disaster relief aid. Education and transportation funding. Loans to small businesses.

But the two-page memo from Matthew J. Vaeth, the acting director of the Office of Management and Budget, left the scope of the pause, and much else, unclear.

Among the uncertainties was whether President Trump has the authority to unilaterally halt funds allocated by Congress. Senator Chuck Schumer of New York, the Democratic leader in the Senate, said in a statement that the memo “blatantly disobeys the law.”

“Congress approved these investments and they are not optional, they are the law,” Mr. Schumer said, adding that “Donald Trump must direct his administration to reverse course immediately and the taxpayers’ money should be distributed to the people.”

In his memo, Mr. Vaeth directed federal agencies to “temporarily pause all activities related to obligation or disbursement of all federal financial assistance,” and any other programs that included “D.E.I., woke gender ideology and the Green New Deal.”