WASHINGTON, March 5 (Xinhua) -- U.S. House Speaker Paul Ryan said on Monday he was "extremely worried" about President Donald Trump's new tariffs on imported steel and aluminum, and urged the president not to move forward with the plan.

Trump announced last Thursday that the United States planned to impose 25 percent of tariff on steel imports and 10 percent for aluminum, as these imports threaten the U.S. national security.

"We are extremely worried about the consequences of a trade war and are urging the White House to not advance with this plan. The new tax reform law has boosted the economy and we certainly don't want to jeopardize those gains," said AshLee Strong, a spokeswoman for Ryan.

Leaders of the U.S. House Committee on Ways and Means have also drafted a letter to Trump, expressing concerns about "the prospect of broad, global tariffs on aluminum and steel imports," according to Lauren Aronson, a spokeswoman for the committee Chairman Kevin Brady.

U.S. trade partners, including Canada and European Union, said that the U.S. actions were unacceptable and they reserved the right to retaliate if the U.S. import restrictions hurt their workers at home countries.

The International Monetary Fund (IMF) said last Friday that the import restrictions announced by Trump would not only hurt the United States, but also other economies.