"Europe is certainly not a threat to American internal security so we expect to be excluded", Malmstrom told reporters before speaking at a conference in Brussels. She will meet US Trade Representative Robert Lighthizer and Japanese Trade Minister Hiroshige Seko in Brussels on Saturday when she will ask whether the European Union is to be included in the tariffs.
The European Union is hoping it will be granted an exemption from USA import tariffs and believes that an exemption for one EU country would apply to the bloc as a whole, European Commission Vice President Jyrki Katainen said on Thursday.
Brussels is also looking at "safeguard" measures to protect its industry - restricting the bloc's imports of steel and aluminium to stop foreign supplies flooding the European market, which is allowed under World Trade Organisation rules.
French President Emmanuel Macron on Friday warned his United States counterpart Trump against forging ahead with the planned tariffs, saying they risked provoking a mutually destructive "trade war".
A WTO spokesman has said they can not comment on the tariff announcement, adding that they are still unclear on the legal basis for the measures.
In Sydney, Prime Minister Malcolm Turnbull cited Washington's strong relationship with Australia, adding: "There is no case for imposing tariffs on Australian steel".
Those threats have been overblown, according to Dani Rodrik, professor of global political economy at Harvard University's John F. Kennedy School of Government and one of the world's leading experts on trade.
Striking a defiant tone, European Commission Vice President Jyrki Katainen called Trump's speech protectionist, saying it remained unclear how a potential exclusion process would work.More news: Police investigating after woman rides horse into Miami nightclub
China's steel and metals associations urged the government to retaliate, citing imports from the USA ranging from stainless steel to coal, agricultural products and electronics.
"To prevent a spiral of protectionism, Germany and the European Union must continue to stand up the global world trade system".
Malmstrom told reporters the European Union was ready to complain to the World Trade Organisation, and retaliate within 90 days.
German Chancellor Angela Merkel urged dialogue and warned that "no one can win in such a race to the bottom".
"We want Congress to understand that this would be a lose-lose situation", he said.
Trade tensions between Washington and Beijing have risen since Mr Trump took office past year.
Beijing vowed to "firmly defend its legitimate rights and interests". Trump has championed coal exports as demand from power firms at home weakens.
South Korea, the third-largest steel exporter to the United States and a strategic ally on the Korean peninsula, called for calm. "It's been planned for several weeks", a Commission official said on Thursday.