President Trump has shut down speculation the US will join talks to revive the Trans-Pacific Partnership, describing the colossal free trade pact proposal with Australia, Japan, New Zealand and eight other nations as a "catastrophe".
The president also slammed Canada for its dairy, timber, lumber and energy trade exports to the US, but he uncharacteristically chose not to criticise China.
Trump's comments came at an Oval Office ceremony on Thursday where, surrounded by steel executives and union leaders, he signed a memorandum ordering an investigation into foreign steel imports and how they threaten US national security.
The 70-year-old said his vow during the election campaign to defend American steel companies and workers was one of the primary reasons for his victory.
"Since the day I entered office I have followed through on that pledge big league, beginning with the withdrawal from the Trans-Pacific Partnership which would have been a catastrophe for our businesses and for our workers," Trump said.
"I'm very proud of that withdrawal.
"Some people say, 'Oh gee, I wish you didn't do that' but the smart people say, 'Thank you, thank you, thank you'."
Japan's Deputy Prime Minister Taro Aso gave life to the TPP this week when he said discussions, without the US, would take place at May's APEC meeting between the remaining 11 nations.
Australian Trade Minister Steven Ciobo has welcomed Japan's renewed interest.
Trump withdrew the US from the TPP just days after his January inauguration.
The new steel import investigation, headed by US Commerce Secretary Wilbur Ross, raises the prospect of new tariffs on steel imports into the US.
"Other countries have made a living taking advantage of the United States in so many ways," Mr Trump said.
Mr Trump's attacks on China's trade policies during campaign speeches, including declaring "we can't continue to allow China to rape our country", were a central plank of his successful election campaign.
The president's tone has changed since he met with Chinese President Xi Jinping at his Mar-a-Lago Florida estate earlier this month.
When asked about China at Thursday's Oval Office ceremony, Trump deflected the question.
"This has nothing to do with China," he said.
"This has to do with worldwide what's happening.
"The dumping problem is a worldwide problem."
Canada and another trade pact, the North American Free Trade Agreement, were among Trump's targets at the ceremony.
"Canada, what they have done to our dairy farm workers, is a disgrace," he said.
"We are going to have to get to the negotiating table with Canada very, very quickly."
