MEXICO CITY (Reuters) – The United States is committing billions of dollars toward development in Central America and Mexico, as part of a plan to strengthen economic growth in the region and curb illegal immigration, the U.S. and Mexican governments said on Tuesday.

Mexican President Andres Manuel Lopez Obrador has been seeking to persuade U.S. counterpart Donald Trump to work with Mexico to develop Honduras, El Salvador and Guatemala, as well as Mexico’s impoverished south, to stem the flow of migrants.

But Trump’s threats to slash aid to the region if illegal immigration were not contained have persistently raised doubts about how much the United States would provide. Much of the new aid pledged on Tuesday will depend on the viability of the projects.

Mexican Foreign Minister Marcelo Ebrard said the United States is committing $5.8 billion toward development in Central America. It is also increasing public and private investment in Mexico by $4.8 billion via the Overseas Private Investment Corporation (OPIC), $2 billion of which is set to go to the south.

Speaking as the U.S. State Department issued a statement setting out the commitments, Ebrard said that the Mexican government had also pledged to find $25 billion to develop the south of the country during the next five years.

“The agreements established here mean more than doubling the foreign investment in the south of Mexico from 2019,” the minister told a news conference in Mexico City.

It was not immediately clear how much of the investment announced represented new funding. A spokesman for Ebrard told Reuters he understood that $2.5 billion of the pledges to develop Central America were fresh commitments.

The State Department said the United States and Mexico would organize a business summit in the first quarter of 2019 to create investment opportunities focusing on southern Mexico and the three Central American countries.

A State Department official who declined to be named said the U.S. pledges include $1.8 billion Washington has spent or allocated between 2015 and 2018, as well as the budget requested for next year. The sums also incorporate OPIC’s current projects and potential pipeline, and the U.S. government’s current Millennium Challenge commitments.

OPIC’s current projects and pipeline for Mexico total $2.8 billion, the official said, adding: “We announced today that OPIC could make another $2 billion available for southern Mexico if commercially viable projects are presented.”