Mr. Trump appears to be taking advantage of the vacuum created by the resignation of Mr. Cohn, who was the plan’s loudest opponent, to push the tariffs through. Mr. Cohn, who argued that tariffs would create a global trade war, found himself overshadowed by a group of more protectionist-minded advisers who have urged the president to follow through with the get-tough pledges he made during his campaign.

Those advisers have been in ascendence, including Mr. Navarro, a trade skeptic who had been sidelined by Mr. Cohn. Mr. Navarro was recently promised a promotion and made the rounds on Sunday talk shows to promote Mr. Trump’s trade policy. Mr. Ross succeeded in moving up last week’s announcement, over the objections of Mr. Cohn. Robert Lighthizer, the United States trade representative who has pushed trading partners to accede to the country’s demands, has become a trusted adviser to the president.

That group has a much more binary view of trade, seeing it as a zero-sum game in which the United States is losing. The advisers have pushed the president to withdraw from trade deals like Nafta and to carry out the type of stiff tariffs that Mr. Trump seems poised to impose on steel and aluminum imports. They see the United States’ ballooning trade deficit, which hit a nine-year high on Wednesday, as evidence that more needs to be done to put the country on the winning end of global trade.

The rise of the populist faction is already fanning fears on Wall Street and among foreign officials that Mr. Trump could start and escalate a global trade war or take a more combative stance toward trading partners and international groups like the World Trade Organization. Foreign officials viewed Mr. Cohn as a reliable ally on global economic issues and as someone who could express their views to the president.

The prospect of approaching tariffs has set off furious lobbying from governments around the world, who have tried to sway the administration with offers of friendship and threats of retaliation. On Wednesday, the European Union released a list of American-made goods it would penalize if the tariffs went through.

China cautioned that it was prepared to “make an appropriate and necessary response” should the United States impose the tariffs.

“Choosing a trade war is a mistaken prescription,” China’s foreign minister, Wang Yi, said during a news conference on Thursday in Beijing. “In the end, you will only hurt others and yourself.”