President Donald Trump is set to make an announcement about new tariffs on Thursday.

But no one, even in the White House, seems to know what to expect.

The confusion suggests a volatile rollout of the massive trade policy.

President Donald Trump is scheduled to sign an order to impose new tariffs on imports of steel and aluminum at 3:30 p.m. ET on Thursday.

The only problem: No one seems to know what he is signing.

The details around the new tariffs, which function as taxes on imports of the metals, have been sparse. It's unclear whether the order Trump will sign Thursday will involve precise legal language or merely a notice of intent.

NBC News' Kristen Welker reported Thursday morning that the exact details of the tariffs were still being worked out and that the signing Thursday could be "symbolic."

Trump offered little specifics while teasing the event on Twitter.

"Looking forward to 3:30 P.M. meeting today at the White House," the president said. "We have to protect & build our Steel and Aluminum Industries while at the same time showing great flexibility and cooperation toward those that are real friends and treat us fairly on both trade and the military."

The Washington Post's Josh Dawsey also tweeted "no one knows" what would be announced.

The chaos over the announcement appears indicative of a rollout rife with discord and confusion.

Before Trump first announced he would impose the tariffs, White House officials told reporters that a White House meeting with steel and aluminum executives was simply a "listening session." Then, midway through talking to reporters last week, Trump announced the tariffs after all: a 25% tax on steel imports and 10% on aluminum imports.

That was only the start of a week filled with uncertainty.

The president's own party was caught off guard. Republicans in Congress said they were blindsided by the move and had been scrambling to persuade Trump to reverse course.

A meeting with business executives who would be harmed by the tariffs was in the works for Thursday and then canceled. Gary Cohn, Trump's top economic adviser, announced his resignation Tuesday in part because of his ideological split from Trump on tariffs.

Even the policy itself has changed wildly depending on the day.

On Wednesday, the White House press secretary, Sarah Huckabee Sanders, said the tariffs would most likely include exemptions for Canada and Mexico for "national security reasons." Sanders said other countries could see similar exemptions.

That represented a significant shift from White House officials' initial rhetoric. As recently as Sunday, the top White House trade adviser, Peter Navarro, said on CNN that "at this point in time, there will be no country exclusions."

Canada and other allies were threatening to respond to Trump's move with trade restrictions of their own.

Politico's Andrew Restuccia reported Thursday morning that details like exemptions were still being worked out. Among the possibilities being considered is a quota, or set limit on the amount of imports, for Canada and Mexico.

Trump added to the confusion during a cabinet meeting on Thursday when he said that "Australia and other countries" could be added to the exemption list. But, the president said, nothing is guaranteed.

"I'm sticking with 10 and 25 initially," Trump said. "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."