NEW YORK (AP) — U.S. stocks are swinging again Wednesday in the final hours before President Donald Trump unveils the tariffs he promised as part of his “ Liberation Day ,” which could drastically remake the global economy and trade.

The S&P 500 was up 0.4% in midday trading after rallying back from an early loss of 1.1%. It’s had a pattern this week of opening with sharp drops only to finish the day higher . The Dow Jones Industrial Average was up 156 points, or 0.4%, after erasing an initial fall of 360 points, and the Nasdaq composite was 0.4% higher, as of 11:30 a.m. Eastern time.

Financial markets around the world have been particularly shaky lately because of uncertainty about what Trump will announce in the event scheduled to begin after the U.S. stock market closes for the day. He has said he wants tariffs to make the global system more fair and to bring manufacturing jobs back to the United States from other countries.

But tariffs also threaten to grind down growth for the U.S. and other economies, while worsening inflation when it may be stuck above the Federal Reserve’s 2% target. Much is still unknown about what Trump will say, including how big the tariffs will be, which countries will be hit and what kinds of products will be targeted. The announcement may also not even clear up all the uncertainty weighing on Wall Street, given that it may just provide a starting point for negotiations with other countries.

One of the hopes that’s helped push upward on the U.S. stock market recently is the possibility that at least the worst of the uncertainty may have already passed.

“We do not know how long the previously enacted tariffs and any future tariffs will remain in force, but we believe peak tariff uncertainty may soon be behind us,” according to Kurt Reiman, head of fixed income Americas, and other strategists at UBS Global Wealth Management. “Much of the work the administration set out to achieve will have been put in place, and there are numerous potential offramps available.”

The tariffs Trump will unveil later in the day will follow other announcements of 25% tariffs on auto imports ; levies against China, Canada and Mexico; and expanded tariffs on steel and aluminum . Trump has also put tariffs against countries that import oil from Venezuela and plans separate import taxes on pharmaceutical drugs, lumber, copper and computer chips.

But even if Wednesday's tariffs end up being less harsh than feared, a worry hitting the market is that the herky-jerky rollout of his trade strategy may itself create enough nervousness to spur U.S. households and businesses to freeze their spending , which would damage the economy.