"We have fully signed and documented another very important part of the Immigration and Security deal with Mexico, one that the U.S. has been asking about getting for many years. It will be revealed in the not too distant future and will need a vote by Mexico’s Legislative body" the president tweeted. "We do not anticipate a problem with the vote but, if for any reason the approval is not forthcoming, Tariffs will be reinstated!"
But Mexico's Foreign Affairs Minister Marcelo Ebrard on Monday said there were no undisclosed parts of the U.S.- Mexico deal.
"Outside of what I have just explained, there is no agreement," Ebrard said at a morning press conference. "It is an immigration agreement, not a commercial one."
The White House did not respond to a question about what the president made reference to, but when asked about Mexico's denial, Trump told reporters Monday, "I don't think they'll be denying it very long."
"We have an agreement on something that they will announce very soon. It's all done," he added, saying it would be announced "at the appropriate time" after Mexico's legislature approves it.
He again threatened tariffs on Mexico if its legislature does not ratify this unknown part of the agreement.
Secretary of State Mike Pompeo backed up Trump's claim, saying, "There were a number of commitments made," but that he couldn't go into details.
On Friday night, after days of talks between U.S. and Mexican leaders, a joint declaration was reached to curb the record number of migrants crossing the southern border. Mexico agreed to deploy its National Guard throughout Mexico to crack down on human smuggling and trafficking, and expand the implementation of existing "Migrant Protection Protocols," a policy that requires migrants to remain in Mexico while their asylum request in the U.S. is adjudicated.
During negotiations the United States also wanted Mexico to agree to a "safe third country" agreement, where asylum seekers would be granted asylum in Mexico and be unable to claim asylum in the US, but Mexico ultimately got the U.S. to back off that request.
Mexico's Ebrard referred to Mexico's resistance to that demand over the weekend and said that the United States began with demands for "drastic measures" but they were ultimately able to reach "middle ground."
The agreement also did not include any promises from Mexico to increase agricultural purchases, which the president tweeted about on Saturday morning.
The president spent the weekend and Monday morning defending the U.S.-Mexico agreement on Twitter against criticisms the deal does not include anything new. Former Department of Homeland Security Secretary Kirstjen Nielsen and Mexico’s Interior Secretary Olga Sanchez had already agreed to deploy Mexican national guard troops to the border during a March meeting in Miami, a Mexican official confirmed to ABC News.
Trump balked at the idea nothing was new and called the report "false and untrue."
Pompeo also spoke to reporters Monday to praise the deal as "diplomacy at its finest," a sign of "the enduring strength too of the relationship between our two countries," and "a significant win for the American people."
"I've seen some reporting that says these countless hours were nothing, that they amounted to a waste of time. I can tell you that the team here at the State Department believes full-throatedly that this is an important set of agreements," he added. "The scale, the effort, the commitment here is very different."
In particular, he said the U.S. ability to now deport asylum seekers to Mexico as their cases are adjudicated will expand to "full throttle" and the deployment of National Guard troops was secured in the meetings and would be Mexico's "biggest effort to date."
Mexico's foreign minister said Monday that their government was already planning to send 6,000 National Guard troops to the Mexico-Guatemala border, but as a result of the deal with the U.S. announced on Friday, that deployment is now happening faster.
The Mexicans were also hesitant about the president's claim that Mexico agreed to a significant increase in Mexican agricultural purchases.
"I want to be quite clear - there is no agreement of any kind that has not been made known," Ebrard said on Monday. "We do not have a specific agreement on products."
The White House and USDA did not respond to a request for comment, however a senior administration official told ABC News there was a "verbal" agreement, although no specifics were discussed.
Some critics said the deal was nothing more than a way for the president to save face after threatening unpopular tariffs against Mexico.
"These are agreements that Mexico had already made, in some cases months ago," Democratic presidential candidate Beto O'Rourke told ABC News' "This Week."
ABC News' Ben Gittleson and Kirit Radia contributed to this report.