President Donald Trump said on Monday the United States had signed another portion of an immigration and security deal with Mexico that would need to be ratified by Mexican lawmakers.
He did not provide details but threatened tariffs if Mexico's Congress did not approve the plan.
"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," Trump tweeted.
"We do not anticipate a problem with the vote but, if for any reason the approval is not forthcoming, tariffs will be reinstated."
Last month, Trump threatened 5% tariffs on Mexican goods. The duties would increase every month until they reached 25% in October, unless Mexico stopped illegal immigration across its border with Mexico.
On Friday, the tariffs were called off, after the United States and Mexico announced an agreement on immigration. The joint communique issued by the two countries provided few details.
Critics have said there have been no new major commitments to slow Central American migrants crossing into the United States.
A White House spokesman did not immediately respond to a request for comment.