MEXICO CITY (Reuters) - Mexico will help to regulate the flow of Central American migrants passing through its territory to the United States, but the root causes behind the phenomenon must be tackled, Mexican President Andres Manuel Lopez Obrador said on Monday.

FILE PHOTO: Mexico's President Andres Manuel Lopez Obrador looks on during a meeting with industry bosses and members of his cabinet to discuss the new administration's policy on the minimum wage at National Palace in Mexico City, Mexico December 17, 2018. REUTERS/Edgard Garrido/File Photo

Speaking after U.S. President Donald Trump on Friday threatened to close the U.S. southern border if Mexico did not halt illegal immigration immediately, Lopez Obrador said he would not have a confrontation with the United States.

“I prefer love and peace,” Lopez Obrador told reporters at his regular morning news conference.

The leftist president has consistently refused to get drawn into a war of words with Trump over the border.

A senior Mexican trade official warned later that closing down the U.S.-Mexico border would cause pain on “both sides.”

Most of the people caught at the frontier trying to enter the United States illegally come from three violent and impoverished countries: Honduras, Guatemala and El Salvador.

Lopez Obrador has tried to persuade Trump to address the problem by fostering economic development in Central America. But on Saturday the U.S. State Department said it was cutting off aid to those three countries. [nL1N21H083]

Detentions at the U.S. border have surged in recent months, angering Trump and putting pressure on Lopez Obrador to find a solution that will prevent a shutdown of the frontier to the market for 80 percent of Mexico’s exports. [nL1N21H06L]

Asked if it was time to put pressure on the Central American countries to do more to tackle the problem, Lopez Obrador said the causes of migration were “not being attended to” and that people needed to be offered more opportunities there.

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“Obviously, we have to help because Central American migrants pass through our territory and we have to bring order to this migration, make sure it’s legal,” he said.

“That’s what we’re doing. But serenely, calmly, without a commotion and with great prudence and responsibility.”

Mexico began issuing temporary humanitarian visas to some members of a migrant caravan in southern Mexico, giving priority to children and the elderly, the National Migration Institute said Monday. It said it would provide transport back to Central American countries, Cuba and Haiti, on a voluntary basis.

Earlier this year, Mexico handed out humanitarian visas liberally, but reined in the program after a surge in applications. The institute said from next month it was planning to encourage people to apply for visas in their home countries.

It was not immediately clear if the government was limiting the number of visas it issues.

U.S. CONGRESSIONAL OBJECTIONS

It has quickly become clear that any plan to cut aid to Central America would face strong objections from members of the U.S. Congress, who must approve it.

One of Trump’s fellow Republicans, Representative Mike McCaul, the top Republican on the House of Representatives Foreign Affairs Committee, said cutting aid would worsen the situation.

“If we cut all this funding ... I think it’s going to make things tragically worse, not better,” he said during a presentation at a think tank in Washington.

Putting a stop to aid to Central America made the job of stemming the flow of migrants tougher, said Senator Ben Cardin, a senior Democrat on the Senate Foreign Relations Committee.

“And closing the border - that makes no sense at all,” he told CNN. “We need Mexico’s cooperation to work with us, and cutting off the border just tells Mexico: ‘We’re doing it alone’.”

Following a meeting on Monday with Lopez Obrador at the Presidential Palace in Mexico City, the Democratic chairman of the House Foreign Affairs Committee, Eliot Engel, invited the Mexican president to visit the committee for a meeting in Washington, an aide to Engel said.

“Excellent meeting with President @lopezobrador_ on importance of U.S.-#Mexico relationship. I emphasized need to partner in assisting Central America,” Engel said on Twitter.

Mexico’s Ambassador to the United States, Martha Barcena, said that the issues of “development cooperation, fighting corruption in Mexico, need for friendly and constructive bilateral relations” were discussed.

U.S. Border Patrol projections are for over 90,000 apprehensions at the border during March, according to data provided to the Mexican government - a more than 140 percent increase from March 2018, and a seven-fold jump from 2017.

U.S. Secretary of State Mike Pompeo said the United States was working with the Central American governments and Mexico and pointed to the numbers when asked why Trump had toughened his stance.

“Just look at the math,” Pompeo told reporters outside the U.S. Army War College in Carlisle, Pennsylvania. “How many folks are coming across. This is a crisis. We need to fix it.”

(This story corrects paragraph 20 to show Engel invited Lopez Obrador for a meeting, not a hearing)