Falling bond yields, further Brexit turmoil, and ebbing confidence in the state of US-China trade talks sent stocks into the red at the open.

But shortly after 1600 GMT, the benchmark Dow Jones Industrial Average was up 0.7 percent, a swing of around 300 points since the morning's dip.

The broader S&P 500 gained 0.5 percent, rising to 2,883.92 while the tech-heavy Nasdaq was up a more modest 0.3 percent at 7,850.37.

"Every time the market fell off the last month, we've seen the buyers show up and curb the selling," Adam Sarhan of 50 Park Investments told AFP.

"With all the negative headlines that we've seen, the market is only 6 percent below its all-time high."

Earlier Wednesday, yields on 30-year Treasury bonds had touched a fresh all-time low while the negative spread between 2-year and 10-year Treasury notes widened the most since 2007, a closely-watched recession indicator.

Meanwhile, British Prime Minister Boris Johnson announced the annual suspension of parliament would be extended until two weeks before a Brexit deadline -- exacerbating fears of a chaotic and potentially damaging exit from the EU.

"A no deal Brexit puts higher odds on Europe entering recession," Alan Skrainka of Cornerstone Wealth Management told AFP, which he said caused the early sell-off.

The US-China trade war remain a concern as well.

"Separately, market participants haven't found much reason to think the US-China trade conflict is going to be resolved soon," analyst Patrick O'Hare wrote at Briefing.com.

Among individual companies, jeweler Tiffany & Co was up 2.6 percent after posting better-than-expected quarterly earnings.