The amendment to the so-called Glacier Law, which was approved by the Senate in February, would make it easier to mine for metals such as copper, lithium and silver in permanently frozen parts of the Andes mountains.

Argentina is a major producer of lithium, which is critical to the global tech and green energy sectors.

If adopted by the Chamber of Deputies in a vote expected late Wednesday, it will become law once signed by Milei.

The amendment has outraged environmentalists, who say it will weaken protections for crucial water sources.

Greenpeace activists scaled a monument in front of Congress at dawn on Wednesday and unfurled a banner urging lawmakers "not to betray the Argentine people."

Seven people were arrested, AFP reported.

Diego Salas, communications director for Greenpeace Argentina, told AFP that the amendment was not only a "betrayal of Argentines" but "a betrayal of humanity because glaciers protect us, they give us life."

There are more than 16,000 glaciers in Argentina.

In the northwest of the country, where mining activity is concentrated, glacial reserves have shrunk by 17 percent in the last decade, mainly due to climate change, according to the Argentine Institute of Snow Science, Glaciology and Environmental Sciences.

- Support from governors -

Milei argues the bill is necessary to attract large-scale mining projects.

According to a Central Bank projection, Argentina could triple its mining exports by 2030.

"Environmentalists would rather see us starve than have anything touched," Milei said when announcing the amendment.

Supporters of the amendment argue that it will clear up ambiguities in the current law.

"We want legal certainty, we want clear definitions," Michael Meding, director of the Los Azules copper mining project in San Juan, told AFP.

The reform has the backing of governors from the Andean provinces, who would have greater latitude to green-light mining projects.

Enrique Viale, president of the Argentine Association of Environmental Lawyers, told AFP that the reform threatened the water supply of "70 percent of Argentinians."

Under the current law, he said, "a scientific body determines the location of glaciers and periglacial environments."

Under the amendment, their location would be "a discretionary decision for each province."