Wilbur Ross, U.S. commerce secretary, speaks during the 47th annual Washington Conference on the Americas at the U.S Department of State in Washington, D.C.

President Donald Trump is opening the door to tariff negotiations with the European Union after exempting Canada and Mexico from new steel and aluminum duties.

"Secretary of Commerce Wilbur Ross will be speaking with representatives of the European Union about eliminating the large Tariffs and Barriers they use against the U.S.A.," Trump tweeted Monday. "Not fair to our farmers and manufacturers."

Earlier Monday, a spokesman for the European Commission said it expects to be in contact with the U.S. "at several levels" this week over steel and aluminum tariffs.

Trump on Thursday signed tariffs of 25 percent on steel and 10 percent on aluminum imports. But he exempted NAFTA partners Canada and Mexico, and the White House will let other nations justify their own case for exception from the tariffs.

The only EU nation in the top 10 sources of U.S. steel imports is Germany, which ranks ninth, according to IHS Global Trade Atlas data for the first nine months of 2017. Canada ranks first and Mexico fourth, the data showed.

Just days after announcing the tariffs on March 1, Trump threatened to impose a tax on car imports from the EU if it "wants to further increase their already massive tariffs and barriers on U.S. companies doing business there."

Last week, the EU threatened to impose duties on U.S. bourbon, peanut butter, cranberries and orange juice if Trump imposed tariffs on steel and aluminum.

— CNBC's Jeff Cox and Reuters contributed to this report.