The U.S. stock market could be on track for its worst day of the year Friday because of turmoil in Greece.
Protesters are rioting in the streets of Athens in opposition to fresh demands for budget cuts and belt-tightening from Greece's European creditors. There are also reports of the resignation of some Greek cabinet members.
This all follows a week of optimistic reports that Greece was on the verge of getting a new bailout package from the IMF, the ECB and the European Commission, while also working out a debt deal with private creditors.
Greek political leaders did agree Thursday on new austerity measures that seemed likely to placate Greece's creditors, but those measures must be put to a vote in Greek parliament over the weekend, and the Greek public is once again expressing its displeasure with being forced to eat another big plate of austerity when the economy is already flat on its back.
Uncertainties about the outcome of all of this are weighing on European stocks, the euro and U.S. stock prices Friday.
The Dow Jones Industrial Average was recently down about 133 points, which is not that awful, but would be the biggest one-day loss of what has so far been a fairly happy year for the blue-chip index.
The S&P 500 was down 0.9 percent and the Nasdaq Composite index was down about 0.8 percent.
The stock market has been drifting higher for months, recently convincing many skeptics, including Dr. Doom himself, Nouriel Roubini, that the rally could be long-lasting. Friday could be a wake-up call, though it is far too early to tell, given this is one day and the mood could brighten considerably over the weekend if Greece passes austerity measures and gets more money.
The euro was down about 0.7 percent against the U.S. dollar as of Friday afternoon.
The yield on the 10-year Treasury note was recently down to 1.96 percent from about 2.04 percent Thursday, an unusually large one-day move, in a sign of investors scrambling for safety -- bond yields fall as bond prices rise.
Though it is generating fewer headlines, news out of China is also affecting sentiment Friday. Chinese imports and exports suffered their first decline in two years last month, and lending fell to a five-year low, reviving worries about a slowdown in that country.
Also souring the mood are the morning's economic data back in the United States: The December trade deficit came in a little wider than expected, and a February reading of consumer sentiment by the University of Michigan was a little lower than expected.