Greece faces a deadline next week for a big loan repayment, and could default if it can't agree with its creditors on what reforms it needs to make.
The Dow Jones industrial average fell 67 points, or 0.4 percent, to 18,076 as of 9:35 a.m. Eastern time Wednesday.
The Standard & Poor's 500 index gave up three points, or 0.2 percent, to 2,120.
The Nasdaq composite decreased 10 points, or 0.2 percent, to 5,150.
Homebuilder Lennar jumped 7 percent after reporting earnings that easily beat the estimates of Wall Street analysts.
