This story was updated at 11:56 a.m. on Wednesday, March 25, 2020, with more information.

NEW YORK (AP) — Stocks are wobbling in tentative morning trading on Wall Street Wednesday,as a historic, worldwide rally downshifts dramatically after just a day.

The S&P 500 drifted up and down in a relatively tight band, a day after packing a year's worth of gains into Tuesday on expectations that Washington was nearing a $2 trillion deal to aid the economy. Tuesday's 11.4% gain for the Dow Jones Industrial Average was its biggest since 1933.

The White House and Senate leaders did announce an agreement early Wednesday, with the Senate possibly voting on it in the afternoon. Investors were anxiously waiting for this kind of aid, which will help blunt the blow to the economy as businesses shut down to slow the spread of the coronavirus.

But even optimists say the package provides just the second leg of three that markets need to regain lasting confidence. The Federal Reserve and central banks are also offering tremendous aid by cutting interest rates and supporting lending markets, but investors say they need to see the number of new infections peak before they can feel comfortable knowing how deep the looming economic downturn will be.

Investors are also still waiting to see the details of Washington's plan, which will include direct payments to most Americans and aid for hard-hit industries. It's unclear when the House of Representatives could vote on the plan.

"The markets are taking it in stride today" after leaping so much the prior day on expectations for the plan, said Darrell Cronk, chief investment officer of Wells Fargo Wealth and Investment Management.

The number of known infections has leaped past 435,000 people worldwide, and more than 19,000 have died, according to Johns Hopkins University. Overall, more than 111,000 have recovered.

For most people, the new coronavirus causes mild or moderate symptoms, such as fever and cough that clear up in two to three weeks. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia and death.

With widening swaths of the economy shutting down and layoffs mounting, economists are sure a steep drop-off is coming. What's unsure is how long it will last.

That uncertainty has led to wild swings in the stock market over the last month. The S&P 500's 9.4% surge Tuesday was a better performance than the index has turned in for 10 of the last 20 full years.

But the market has also had a couple days within the last few weeks that packed entire years' worth of losses, including two days down 10.4%. The S&P 500 has not had a back-to-back gain since the sell-off began on Feb. 20, a day after the index set its record. Stocks are down about 28.5% since then.

The uncertainty has carried over even to trading within a certain day or a certain hour.

The S&P 500 was up 0.6%, as of 11 a.m. Eastern time. Earlier in the morning, it was up as much as 2.2% and down as much as 1.6%. The Dow was up 452 points, or 2.1% largely because of a big jump for a single stock, Boeing.

European markets initially jumped to strong gains, but they faded as the day progressed. Germany's DAX was down 1.2%, and the French CAC 40 was up 0.8%.

Earlier on Wednesday, Asian markets surged to big gains following the big U.S. day. Asia, Japan's Nikkei 225 jumped 8%, South Korea's Kospi rose 5.9% and the Hang Seng in Hong Kong gained 3.8%.

Echoing the subdued trading in the stock market, Treasury yields were holding relatively steady. The yield on the 10-year Treasury dipped to 0.80% from 0.81% late Tuesday.