Wall Street opens lower on Greece worries

"If the Fed keeps delaying and doesn't start the process of a rate hike, they are going to lose credibility," said Rick Meckler, president of LibertyView Capital Management in Jersey City, New Jersey, which oversees about $1 billion. Investors also keep an eye on Greece, which must repay four loans totaling 1.6 billion euros ($1.8 billion) to the International Monetary Fund this month, starting with a 300 million euro payment on June 5.