Secretary of State Marco Rubio confirmed he's the acting administrator at USAID and expressed his concerns with the agency on Monday.

"My frustration with USAID goes back to my time in Congress," Rubio, a former senator, told reporters during his diplomatic trip to Central America. "It's a completely unresponsive agency."

"It's supposed to respond to policy directives of the State Department, and it refuses to do so. So the functions of the USAID -- there are a lot of functions of USAID that are going to continue, that are going to be part of American foreign policy but it has to be aligned with American foreign policy."

Secretary of State Marco Rubio has been made acting administrator of USAID, multiple sources told ABC News.

The news comes amid turmoil at the agency and is the latest step in the Trump administration's effort to move USAID under the State Department.

-ABC News' Will Steakin, Alexander Mallin and Shannon Kingston

President Donald Trump confirmed Mexican President Claudia Sheinbaum's announcement that tariffs have been paused for one month. He said negotiations between his administration officials and Mexico will continue in the interim.

"I just spoke with President Claudia Sheinbaum of Mexico. It was a very friendly conversation wherein she agreed to immediately supply 10,000 Mexican Soldiers on the Border separating Mexico and the United States," Trump wrote on Truth Social.

"These soldiers will be specifically designated to stop the flow of fentanyl, and illegal migrants into our Country. We further agreed to immediately pause the anticipated tariffs for a one month period during which we will have negotiations headed by Secretary of State Marco Rubio, Secretary of Treasury Scott Bessent, and Secretary of Commerce Howard Lutnick, and high-level Representatives of Mexico. I look forward to participating in those negotiations, with President Sheinbaum, as we attempt to achieve a 'deal' between our two Countries."

The shift comes a few days after Trump said there was "nothing" either Canada or Mexico could do to stop the tariffs. At the time, he acknowledged there might be some initial disruptions to the economy but argued it would be worth it in the long term. On Monday, before the announcements from Mexico and the U.S. on a pause, the tariff threat had sent the stock market falling.

Mexican President Claudia Sheinbaum said in a social media post that, after a conversation with President Donald Trump, tariffs "are paused for a month from now" after several agreements.

Sheinbaum wrote those agreements include Mexico reinforcing the border with 10,000 National Guard troops to prevent drug trafficking and the U.S. committing to work on preventing "high-powered weapons" from crossing into Mexico.

"Our teams will start working today on two fronts: security and trade," she wrote on X.