MEXICO CITY (Reuters) - Mexico, a top shipper of steel to the United States, will wait to see if U.S. President Donald Trump announces tariffs on steel and aluminum imports before reacting, President Claudia Sheinbaum said on Monday.

Trump is expected to introduce new 25% tariffs on Monday on all steel and aluminium imports into the United States, on top of existing metals duties, in another major escalation of his shake-up of trade policy.

"We're going to wait to see if anything is announced today, and from there we'll make a decision," Sheinbaum said in her daily morning press conference, adding she would keep a "cool head."

Sheinbaum has taken a measured approach in dealing with Trump's tariff threats so far, urging calm instead of reacting rashly.

Mexico's economy ministry met with steel industry leaders last week, saying it would work with them to strengthen national production as part of a government investment roadmap.

The ministry also rolled out a mechanism to better track steel imports and exports as well as their countries of origin "to prevent disloyal practices in the steel trade," it said in a statement.

U.S. steel companies as well as Trump's administration, and the Biden administration before it, have accused Mexico of flooding the market with steel imports.

U.S. trade officials have previously demanded more transparency in the origins of Mexico's steel products, as they argue China has been accused of selling surplus steel abroad at below-market prices, a practice known as dumping.