WASHINGTON (Reuters) — Mexican President Andres Manuel Lopez Obrador pitched a tree-planting jobs program in Central America that he said should lead to U.S. work visas, in talks with Vice President Kamala Harris on Friday about root causes of migration.

At the start of the call, Harris said the United States and Mexico must fight violence and corruption together, to help diminish migration from Central America.

“Most people don’t want to leave home and when they do it is often because they are fleeing some harm or they are forced to leave because there are no opportunities,” said Harris.

Lopez Obrador, 67, said he had a specific proposal he wanted to discuss with Harris. He did not give details, but told reporters minutes earlier that the tree planting idea was at the top of his mind.

“We agree with the migration policies you are developing and we are going to help, you can count on us,” he said.

The Mexican leader told reporters at a news conference Friday morning that legal routes were the best solution to migration.

“If there’s a regular, normal and orderly migratory flow, we can avoid the risks migrants take who are forced to cross our country,” he said.

The trees-for-visas proposal was met with some surprise when Lopez Obrador previously raised it at a Washington climate summit in April.

President Joe Biden has entrusted Harris with leading efforts to cut immigration from Mexico and Central America’s “Northern Triangle” countries – Guatemala, Honduras, and El Salvador – as the administration grapples with an increase in people crossing into the United States at the southern border.

Harris has said she will visit Mexico and Guatemala on June 7-8, her first foreign trip as vice president.

The Biden administration has made the rule of law, judicial independence and the fight against corruption prominent elements of its strategy to improve conditions in Central America.

Lopez Obrador rose to prominence criticizing corruption in past governments and considers the issue central to his legacy.

However, shortly before Friday’s call his government made a formal diplomatic complaint to the United States for financially supporting an anti-graft group he considers to be politically opposed to the government.

Lopez Obrador said the issue would not be raised in the meeting with Harris. He also said he would not stay for the entire call.

Lopez Obrador, who touted his good relations with both the previous Trump administration and the current Biden administration, has taken a harder line with Washington on a range of issues in recent months.

Asked what Harris hoped to accomplish in the talks and what if any agreements were expected, Ricardo Zuniga, the U.S. special envoy on Central America’s Northern Triangle countries, said on Wednesday that the discussions would delve into immigration but also go beyond that issue.

“We’re undertaking these kinds of engagements with the view of the totality of our relationship with Mexico in mind,” Zuniga said. “Mexico is our largest trading partner… We’re deeply connected to them through economics and, through… our value chain and production chains.”

Reporting by Nandita Bose in Washington; Additional reporting by Matt Spetalnick and Ted Hesson in Washington, and Raul Cortes Fernandez in Mexico City; Editing by Grant McCool and Alistair Bell.