(CNN) The Trump administration has put a temporary hold on the majority of congressionally approved foreign aid funds, pending a review by the State Department and the US Agency for International Development. Critics say the move undercuts Congress and fear that it is another attempt by the administration to cancel aid programs that advocates see as vital to US interests.

The Office of Management and Budget informed the two agencies in a letter Saturday that unobligated funds would be frozen until "three business days after" State and USAID provide an accounting of how much remains in specific accounts and how the funds are being spent. Those funds expire on September 30, the end of the fiscal year.

Secretary of State Mike Pompeo was out of the country when the letter, addressed to Deputy Secretary of State John Sullivan, was sent. Congress was on recess.

A USAID official told CNN the funding amounts to between $2 billion and $4 billion.

The accounts specified in the letter include funding for international organizations, international peacekeeping, international narcotics control and law enforcement, global health, development assistance, foreign military and assistance for Europe, Eurasia and Central Asia.

The Washington Post was the first to report on the letter.

A senior administration official told CNN that "if an agency can't even tell us how much money is in the account, I have no confidence in their ability to tell me where the money is going to go to."

Based on the responses from the agencies, OMB may propose to Congress canceling the appropriated funds, which is known as rescission, or reprogramming them.

The USAID official told CNN that "it is pretty clear they will try to rescind the money." That official noted that OMB made a similar attempt last year but Congress rejected the move.

The review will take several days, the official said, and it is expected that the tally will be sent to OMB by early next week at the latest. However, the official noted that if OMB decides to maintain the freeze in an effort to cancel any of the foreign aid, it could take a while to get the funding streams open because it would require action from Congress.

"It'll be a long process," said the official.

A senior administration official told CNN that "the accounts that are being looked at include programs that many over the years have considered wasteful like ones that would pay for solar panels in the Caribbean, a space program in Pakistan, soccer camps in Guatemala, and foreign aid to countries that aren't in the best interest of US foreign policy."

Liz Schrayer, the president of the US Global Leadership Council, condemned OMB's action as "reckless and irresponsible."

"These are programs that are in our interest," she told CNN. "If we take ourselves off the playing field, we do it at our own peril. These are programs that we are using to advance our economic and our security interests and I think it is really surprising that the administration is pulling back on what is less than 1% of our entire budget when there are such great threats in the world."

In a statement, Rep. Eliot Engel, the chairman of the House Foreign Relations Committee, called the move a "dangerous action" and vowed to reverse any rescission or reprogramming.

"This Administration's contempt for Congress is astounding. When Congress decides how much we spend on foreign assistance, it isn't a suggestion. It's the law, backed up by the constitution," the New York Demcrat wrote in a statement. "President Trump and Secretary Pompeo should follow the law and stop playing politics with our foreign affairs budget. If they move ahead with this plan, I'll use the full power of the Foreign Affairs Committee to reverse their efforts and to demand answers about why this Administration seems determined to ignore the will Congress and undermine American leadership."

The State Department and USAID referred CNN to OMB for comment.

"It is incumbent on all Federal agencies to properly use funds provided by Congress. In an effort to ensure accountability, OMB has requested the current status of several foreign assistance accounts to identify the amount of funding that is unobligated. On behalf of American taxpayers, OMB has an obligation to ensure their money is being used wisely," OMB spokesperson Rachel Semmel said in a statement.