(CNN) President Donald Trump's decision to follow through on steel and aluminum tariffs against some of the United States' closest allies puts a series of vulnerable Republicans at considerable risk, leading some of those candidates to caution the President against following through with the trade talk.

Commerce Secretary Wilbur Ross told reporters that a 25% tariff on imported steel and 10% on imported aluminum from Canada, Mexico and the European Union will take effect on Friday.

Mexico announced in a statement Thursday it would retaliate against the US by imposing "equivalent measures" on products such as "flat steel, lamps, pork and numerous produce items until the US eliminates the imposed tariffs."

Some Republicans are worried. Party operatives told CNN Thursday that they are fretting the ramifications of more trade talk, worried that those countries could respond by targeting key US exports, many of which come from districts that could decide the balance of the House in November.

"Trade is an area where President Trump's thinking and policy differs profoundly from most other Republicans," said longtime Republican operative Michael Steel.

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