SAO PAULO/MEXICO CITY (Reuters) - E-commerce giants Amazon.com ( AMZN ) and MercadoLibre ( MELI ) stand to benefit from new tariffs on low-cost imports into Mexico over Asian retailers like Shein and Temu, according to analysts at Itau BBA.

Mexico this month imposed a 19% tax on imports via courier services from countries with which it does not have a free-trade agreement, which includes China.

Imports from the U.S. and Canada, part of a regional trade agreement with Mexico, will be exempt on purchases worth under $50. Items worth between $50 and $117 coming from the U.S. and Canada will face a 17% duty.

"The policy seems primarily targeted at Asian players like Shein and Temu, which previously benefited from exemptions on imports below $50," analysts at Itau BBA wrote in a note sent to media on Tuesday.

The measures come amid heightened trade tensions with the U.S. President-elect Donald Trump, who campaigned on a promise to impose stiff tariffs, including on Mexico and Canada, doubled down on the threat on Tuesday, promising "very serious" tariffs on the two countries. 

Trump has previously accused Mexico of being a backdoor for Chinese goods, which Mexico has denied. Still, Mexican officials recently launched "Operation Clean-Up" to seize contraband goods sent into the country from Asia.

Amazon ( AMZN ) stands to gain the most from the changes, according to the Itau BBA team, followed by MercadoLibre ( MELI ).

Around 30% of goods sold by Amazon ( AMZN ) in Mexico are shipped in, mostly from the U.S., according to Itau BBA.

MercadoLibre ( MELI ) brings in some 15% of its goods sold in Mexico from abroad, largely from China, Itau BBA said. 

While the tariffs will impact MercadoLibre's ( MELI ) goods sourced from China, "the overall effect should be net positive" on the reduced competition, the analysts wrote.

Mexico last month announced a 15% tariff on imports of raw textiles and 35% on finished fabric-based products like clothing, curtains and blankets.

"Some companies used loopholes to import finished products, primarily from China, to redirect these goods to the local market," Itau BBA said, arguing the strategy had disrupted fair competition in the local market. 

Both MercadoLibre ( MELI ) and Amazon ( AMZN ) should continue strengthening their foothold on Mexico and are "growing fast," Itau BBA said.

(Reporting by Patricia Vilas Boas in Sao Paulo and Kylie Madry in Mexico City)