Internal communications reviewed by ABC News show that the Trump administration plans to strictly implement an executive order from the president mandating a 90-day freeze on almost all U.S. foreign aid amid a review, a measure that already has sparked widespread concern among humanitarian organizations.

"We get tired of giving massive amounts of money to countries that hate us, don't we?" President Donald Trump said in a speech during the House Republicans' annual retreat in Florida on Monday, touting a blizzard of executive actions he had taken since returning to the White House.

In a memo sent to U.S. Agency for International Development (USAID) staff over the weekend, a high-level official within the agency stressed their "responsibility" to carry out Trump's directive and signaled that it would be difficult to secure waivers to continue funding for programs during the pause, which he called "a complete halt."

"It is important to emphasize that it is no longer business as usual. Every program will be thoroughly scrutinized," Ken Jackson, USAID's assistant to the administrator for management and resources, wrote.

Jackson said that the agency's only exceptions currently in place covered spending on emergency humanitarian food aid and travel for government officials who were returning to their duty stations, adding that employees should be ready "to provide detailed information and justification" for these expenses.

Any waivers for other spending would need to clear multiple hurdles for approval, including proving that the program receiving funding was lifesaving or necessary for U.S. national security.

Failure to comply with the pause or other new policies "will result in disciplinary action," Jackson warned USAID staff.

That warning was not an empty threat. Late Monday, multiple sources said that nearly 60 senior USAID officials had been placed on leave, including nearly all senior attorneys for the agency.

According to an email obtained by ABC News, acting USAID administrator Jason Gray accused the agency of skirting Trump's executive orders but provided no information about the alleged violations.

"We have identified several actions within USAID that appear to be designed to circumvent the President's Executive orders and the mandate from the American people," Gray wrote in the email. "As a result, we have placed a number of USAID employees on administrative leave with full pay and benefits until further notice while we complete our analysis of these actions."

A separate memo sent to State Department employees last week which was also reviewed by ABC News instructed officials overseeing projects funded by grants and awards that have already been distributed to issue immediate "stop-work orders," making exceptions for some travel and administrative expenses, emergency food aid, and foreign military financing to both Egypt and Israel.

An administration official said on Monday that a template for submitting waiver requests had been made available and that the State Department was reviewing numerous applications that had already been submitted, but could not give a timeline for when any decisions would be made.

The State Department officially announced the implementation of the freeze on Sunday.

"Secretary Rubio has paused all U.S. foreign assistance funded by or through the State Department and U.S. Agency for International Development (USAID) for review," the department's spokesperson, Tammy Bruce, said in statement. "He is initiating a review of all foreign assistance programs to ensure they are efficient and consistent with U.S. foreign policy under the America First agenda."

By then, panic had already set in among international aid groups that rely on U.S. funding. Sources within the international community said the freeze was so expansive that they could hardly believe it was real.

"The recent stop-work cable from the State Department suspends programs that support America's global leadership and creates dangerous vacuums that China and our adversaries will quickly fill," InterAction, the largest alliance of international aid organizations, said in a statement.

"This halt interrupts critical life-saving work including clean water to infants, basic education for kids, ending the trafficking of girls, and providing medications to children and others suffering from disease. It stops assistance in countries critical to U.S. interests, including Taiwan, Syria, and Pakistan. And, it halts decades of life-saving work through PEPFAR that helps babies to be born HIV-free," the statement continued.

Beyond concern for their work, some organizations and officials have also expressed confusion. Many were caught off guard by the State Department's implementation of Trump's order, which they initially believed wouldn't impact programs funded through congressional appropriations.

"The aid community is grappling with just how existential this aid suspension is - we know this will have life or death consequences for millions around the globe, as programs that depend on this funding grind to a halt without a plan or safety net," Abby Maxman, the president and CEO of Oxfam, said in a statement to ABC News.

"This decision must be reversed, and funding and programming must be allowed to move forward. But at the very least, the administration must communicate clearly so the aid community can plan for the future and determine how to carry on our lifesaving work," Maxman added.

Critics of the freeze believe dissent from international aid organizations and U.S. officials has been muted due to fear of retribution from the administration.

In his memo to USAID employees, Jackson stipulated that one of the new policies they must comply with if they wished to avoid disciplinary action was a requirement that all external communication, including with the State Department, first be approved by the agency.