BUENOS AIRES (Reuters) - Argentina's benchmark S&P Merval stock index tumbled close to 4% on Monday, after libertarian President Javier Milei touted a cryptocurrency which crashed soon after, in a case the country's fintech chamber said could amount to a "rug pull."

Milei later deleted his X post recommending the little-known crypto coin $LIBRA and said he had no relation to the cryptocurrency, but opposition lawmakers have said Milei could face an impeachment trial in Congress.

A judge was assigned to evaluate the legal cases against Milei on Monday.

Analysts said the opposition is unlikely to garner the votes to push through an impeachment proceeding but the accusations of fraud and Milei's direct involvement should have an important political impact on his government, which faces mid-term elections later this year and has championed taking a chainsaw to red tape.

Some investors reacted on social media over the weekend in anger, saying they had been scammed out of their savings by the president of Argentina, while Milei's supporters defended him as the victim of politically-motivated attacks.

"Irresponsible promotion of assets puts thousands of people at risk," ONG Bitcoin Argentina, a local educational non-profit, said over the weekend. "We take a stand against this fact and reaffirm the importance of education and transparency."

In a regular morning conference, Mexican President Claudia Sheinbaum responded to questions on the scandal saying the public would have to see what comes out of the investigations.

"It is extremely serious if confirmed, especially in terms of a president's powers to promote something private," she said. "If as a president of a country you propose something for private benefit there is an obvious conflict of interest."

Milei himself came out swinging in face of criticisms.

"To the filthy rats of the political caste who want to take advantage of this situation to do harm, I want to say that they confirm every day how vile politicians are, and this increases our conviction to kick them in the ass," Milei said in a post on Friday in which he said he had deleted his original post.