(CNN) -- Confusion abounded late Wednesday in the West Wing over President Donald Trump's impending trade announcement rolling out tariffs on steel and aluminum imports.
White House aides had been told to prepare for a signing ceremony Thursday at 3:30 p.m. ET in the Roosevelt Room, where steel and aluminum workers also are set to attend. But one White House aide said Wednesday night that the event had been canceled -- because the policy was not yet finalized.
As of late Wednesday evening, the tariff announcement was not listed on the White House schedule.
White House trade adviser Peter Navarro said in a TV interview Wednesday night that Mexico and Canada would be exempt from the tariffs, reinforcing the possible exemption that press secretary Sarah Sanders had mentioned at the White House briefing in the afternoon.
"There are potential carve-outs for Canada and Mexico based on national security, and possibly other countries as well," Sanders had said. She said the national security exemption would be on a "case-by-case" and "country-by-country" basis.
"Within about 15 to 30 days the tariffs go into effect," Navarro said in the Fox Business interview. "The proclamation will have a clause that does not impose these tariffs immediately on Canada and Mexico, and it's going to give us an opportunity ... to negotiate a great deal for this country, then all is good with Canada and Mexico."
Still, the policy and timing were unclear.
Another aide said the event was still on -- as far as they knew.
A third aide, who is drafting the tariffs, had this to say when asked whether it will be rolled out Thursday: "I'm not totally sure."
This aide added that they're planning to pull an all-nighter, after consulting with numerous Cabinet secretaries.
"It's absurd," the aide said. "Absurd."
Trump had applied pressure on his staff to complete the tariffs before the end of this week, hoping the announcement can help him rally voters behind the Republican candidate in a Pennsylvania special election next week in the state's 18th Congressional District. Trump is due to campaign for the GOP candidate, Rick Saccone, on Saturday.
The potential tariffs have caused deep anxiety among US trading partners and Republican leaders in Congress.
Trump announced the tariffs last week during a meeting with industry executives, sending his aides into a scramble to fully vet the legality of the tariffs and finalize the language.
CNN's Kevin Liptak contributed to this report.
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