The order came at the start of a long congressional recess, but lawmakers are asking the State Department about the decision. A senior Democratic aide said on Tuesday that Congress had allocated the funds to protect national security interests. The move would set a precedent for future administrations to ignore spending bills and eliminate spending obligations, the aide said, speaking on the condition of anonymity because members of Congress were still determining how to respond.

A spokeswoman for the budget office, Rachel Semmel, said that federal agencies had a responsibility to properly use the money provided by Congress. “ In an effort to ensure accountability, O.M.B. has requested the current status of several foreign assistance accounts to identify the amount of funding that is unobligated,” she said.

A State Department representative acknowledged the review and said only, “No decision has been made on what will be done with those funds.” Additional questions were referred to the Office of Management and Budget.

The New York Times obtained a copy of the office’s letter on Tuesday. The Washington Post first reported on the letter on Monday.

The Trump administration has proposed drastic cuts to foreign aid in all its budget proposals, but Congress has rejected those moves each time. President Trump has criticized foreign aid in general, cutting aid to Palestinian refugees and three Central American countries, among others. He has said the Central American nations must prevent their citizens from trying to migrate to the United States.

After the review, the Office of Management and Budget could return money for projects it considers unnecessary to the Treasury Department, in a process known as rescission. The office would send a rescission package to Congress, which would then have 45 days to decide whether to approve ending the funds.

The office’s gambit is based on timing, its critics say. Congress is in recess until Sept. 9, so even if it rejects a rescission package, the State Department and U.S.A.I.D. will have only until the end of that month, when the fiscal year ends, to designate the funds.