The agency takes US taxpayers' money and spends it as a global charity, without regard for whether it is in the national interest or not, he said, calling USAID a disappointment to the government.
US President Donald Trump has repeatedly criticized USAID, saying that it spends US taxpayer money on projects that do not serve US interests.
On Monday, Trump appointed Rubio as acting head of USAID, who in turn notified Congress of a review of the agency's foreign aid.
CBS reported on Monday, citing sources in the know, that USAID will merge into the State Department and undergo workforce reductions while still retaining its commitment to humanitarian efforts.
The Trump administration is expected to make an official announcement about the move in the coming days while discussions of funding reductions are still ongoing, the report said.
Rubio had previously said that the decision to merge USAID with the State Department was not aimed at ending its programs but was related to problems in its management.
Earlier on Monday, CNN reported that employees of the USAID headquarters in Washington have received an email from the management stating that the office will be closed on Monday and that they should not come in.
On Saturday, the USAID website went down and to date remains unavailable.
The White House announced last month that Trump had signed an executive order suspending development assistance to other countries for 90 days to assess whether those programs were consistent with US foreign policy.
US billionaire entrepreneur and the head of the newly established Department of Government Efficiency, Elon Musk, said on Monday that President Donald Trump had agreed to shut down USAID.
On Sunday, Musk called USAID a "criminal organization" that "needs to die." In a separate post on X, he described the agency as a "nest of radical left-wing Marxists who hate America."