By Alberto Alerigi

SAO PAULO (Reuters) - Brazilian steelmaker Gerdau may opt to bump up its output capacity in the United States instead of building a new plant in Mexico, its CEO said on Thursday, as tariffs implemented by President Donald Trump shake up global trade.

Gerdau announced last year it was considering installing a new special steel mill in Mexico, which would have an annual capacity of some 600,000 metric tons and require investment of $500 million to $600 million.

Gerdau initially expected to reach a final investment decision by the end of 2024 to start building the plant this year, but it has now postponed the decision until July.

"We are reviewing all our analyses in light of what is happening," Chief Executive Gustavo Werneck told an earnings call. "Special steel is a very important segment for us in the Americas."

"We are looking at the possibility of building the mill in two stages, or increasing production capacity in the United States," Werneck said, citing the company's units in Michigan and Arkansas.

U.S. President Trump earlier this month substantially raised tariffs on steel and aluminum imports to a flat 25% "without exceptions or exemptions," adding to other tariff threats against major trading partners such as Mexico and Canada.

Gerdau stands to benefit from the tariffs, as it operates production units in the U.S., and had previously touted its substantial footprint in the country as a hedge against the risk of protectionism from Trump.

Werneck said the tariffs should lead to a better production mix in the U.S. and higher profitability.

The firm is currently operating at 70% of its rolling capacity in the U.S., or about 4 million tons per year.

Gerdau, Brazil's largest steelmaker by market capitalization, on Wednesday posted a 9% decline in its fourth-quarter adjusted net profit from a year earlier, landing below market expectations.

The firm, which owns mills across the Americas, said that starting from the first quarter of 2025 it would segment its earnings out by regions - Brazil, North America and South America.

"Gerdau North America should be a clear winner - at least in the near-term - following the steel tariffs announced by President Trump," analysts at Scotiabank said, although noting the Brazilian unit could be negatively impacted.

Sao Paulo-traded shares in Gerdau rose 0.7% on Thursday, in line with the broader Bovespa stock index.

(Reporting by Alberto Alerigi Jr.; Writing by Gabriel Araujo;Editing by Elaine Hardcastle)