The S&P 500 rallied for a second straight session on Wednesday as the U.S. Senate appeared to near a vote on a $2 trillion package to support businesses and households devastated by the coronavirus pandemic.

Wall Street trimmed hefty gains late in the session after reports raised doubts about how quickly the bill might pass, but the S&P 500 and Dow Jones Industrial Average still ended up more than 1% and 2%, respectively.

Boeing surged 24%, bringing its gain over the past three sessions to almost 70% as investors bet on government support for the aerospace industry as well as airlines. American Airlines Group, United Airlines Holding and Delta Air Lines each jumped more than 10%.

Boeing, long a symbol of U.S. manufacturing strength, remains down by more than 50% since mid-February.

It was the first time since Feb. 12 that S&P 500 climbed two days in a row.

"What the fiscal and monetary stimulus has done is to allow the market to recover," said Justin Hoogendoorn, head of fixed income strategy at Piper Jaffray in Chicago. "It's not because the main street community is coming back. It's the institutional crowd being able to say, 'the world isn’t falling apart'."

Top aides to Republican President Donald Trump and senior Senate Republicans and Democrats said they had agreed on the unprecedented stimulus bill, which includes a $500 billion fund to help hard-hit industries and a comparable amount for direct payments of up to $3,000 apiece to millions of U.S. families.

However, Senator Bernie Sanders, an independent who is running for the Democratic presidential nomination, said he was prepared to put a hold on the bill unless a group of Republican senators drop their objections to language on jobless benefits in the legislation.

Top House Republican Kevin McCarthy said he wanted House members to have at least 24 hours after the Senate vote to review the bill.

With fears of a global recession and corporate defaults running high, and expectations of a continued surge in coronavirus cases in the United States, many investors remained reluctant to call an end to Wall Street's recent, staggering selloff.

"We are still in a phase where we need to be cautious," warned Rob Haworth, senior investment strategist for U.S. Bank Wealth Management. "We don't yet know when these social distancing measures will end, and the evidence for now is that they will continue to expand."

Data due on Thursday is likely to show U.S. weekly jobless claims surging to 1 million as companies announce layoffs and as state-wide lockdowns force businesses to shutter stores.

The Dow Jones Industrial Average rose 2.39% to end at 21,200.55 points, while the S&P 500 gained 1.15% to 2,475.56.

The Nasdaq Composite dropped 0.45% to 7,384.30, giving up its earlier gains.

GLOBAL MARKETS

The dollar slid and global equity markets marched higher for a second day of gains, on optimism $2 trillion in U.S. fiscal stimulus will dampen the economic shock the coronavirus pandemic has started to inflict.

Europe's main markets in London, Frankfurt and Paris struggled to stay positive after ripping 4%-5% higher. Oil prices swung from 3% up to 3% down. Wall Street also teetered, though the Dow industrials and S&P 500 mostly remained more than 1% higher while the Nasdaq closed lower.

MSCI's gauge of stocks across the globe gained 2.88% and emerging market stocks rose 4.40%.

The pan-European STOXX 600 index rose 3.09%.

In the currency markets, the dollar slipped for a third straight session as a scramble for liquidity was soothed by the super-sized U.S. stimulus plan.

The dollar index fell 0.757%, with the euro up 0.92% to $1.0886. The Japanese yen strengthened 0.03% versus the greenback at 111.20 per dollar.

The risk-sensitive Australian dollar jumped over the 60-U.S. cent mark for the first time in a week.

Bond markets were also calmer. Benchmark U.S. Treasuries were yielding 0.7987% while in Europe Germany's 10-year yield edged a basis point higher to -0.296%, tailed by other higher-rated government debt.,

European Central Bank chief Christine Lagarde asked euro zone finance ministers during a videoconference on Tuesday to seriously consider a one-off joint debt issue of "coronabonds," officials told Reuters.

In metals markets, gold changed hands at $1,608.78 an ounce , retaining most of Tuesday's gains of almost 5%, its biggest jump since 2008.

U.S. crude prices rose slightly, bolstered by progress on a massive pending U.S. economic stimulus package.

Brent crude gained 24 cents to settle at $27.39 a barrel. U.S. crude futures rose 48 cents to settle at $24.49 a barrel.

U.S. gold futures settled 1.5% lower at $1,634.90 an ounce, a day after posting their biggest one-day jump since 2009.