Stocks are sliding

US stocks are tumbling on Monday as the market looks ahead with uncertainty to the US presidential debate and OPEC's informal meeting in Algiers.

At 12:10 p.m. ET, the Dow was down 143.85 points (-0.79%), the S&P 500 was lower by 14.29 points (-0.67%) and the Nasdaq was off 40.91 points (-0.77%).

The financial and healthcare sectors of the S&P 500 led declines, each down 1.1%.

Deutsche Bank shares slumped 6.5% to a record low after reports surfaced over the weekend that German Chancellor Angela Merkel will not provide state assistance to the troubled bank.

Elsewhere, Twitter is down nearly 3.00% to $21.96 per share after Oppenheimer research analyst Jason Helfstein said a takeover of the company doesn't make sense with the stock priced at these levels. On Friday, the stock surged 22% on word of a a potential acquisition.

In the commodities space, West Texas Intermediate crude oil gained 3.28%, rallying to $45.94 per barrel as OPEC talks begin and the Algerian Energy Minister claims that all options are on the table for an output cut or freeze.

Meanwhile, US Treasurys rose, pushing the benchmark 10-year yield down 5 basis points to 1.57%. The Treasury Department is set to sell $26 billion in two-year notes at 1 p.m. ET.

In economic data, new home sales dropped less than expected in August, falling 7.6% to a an annually adjusted 609,000. That was smaller than the 8.3% drop that was expected by the Bloomberg consensus.