President Donald Trump plans to sign a proclamation enacting steel and aluminum tariffs at a Thursday meeting following a week's worth of controversy over his plans to impose the new penalties, the White House said just hours before the event.

Trump first announced the meeting — which had not previously been listed on the White House's official schedule — Thursday morning on Twitter, saying that new protections for these industries would show "great flexibility and cooperation toward those that are real friends and treat us fairly on both trade and the military.”

In the immediate aftermath of the tweet, it was still unclear — even to many within the administration — precisely what would happen at the 3:30pm event, a White House official told NBC News. Mid-afternoon, the administration announced that the president would use the event to officially move forward on the new policy.

Trump reiterated his desire to levy tariffs of 25 percent on steel and 10 percent on aluminum products at a Cabinet meeting Thursday, but told reporters that the U.S. would be "flexible" in their application, adding Australia to the list of allied nations that could see some sort of exemption from the penalties.

On Wednesday, the White House said Canada and Mexico would likely get carve-outs on the tariffs.

"I’ll have a right to go up or down, depending on the country and I’ll have a right to drop out countries or add countries. We just want fairness," Trump said Thursday.

While the White House has repeatedly said these tariffs should come as no surprise, the news has riled many GOP lawmakers, U.S. trade partners, and even some inside Trump's own White House. National Economic Council Director Gary Cohn resigned Tuesday following the president's unexpected announcement that he planned to enact the trade penalties.

On Thursday, Trump praised and knocked Cohn in the same breath, saying he was "terrific" despite being "a globalist... but in his own way he's a nationalist, because he loves our country."

Cohn, a former Goldman Sachs banker and a registered Democrat from New York, was tagged as a "globalist" by detractors in and outside the White House who used it pejoratively to signal that he was opposed to Trump's more populist or "nationalist" economic message during the 2016 campaign.

Trump predicted that Cohn, on hand for Thursday's Cabinet meeting, would "maybe come back" to the administration making "another couple of hundred million" dollars in the private sector, though he wouldn't come back to the same role as a top economic advisor because "he's not quite as strong on those tariffs as we want."