Anticipation over the pending expiration of a Greek bailout package sent crude oil prices again into negative territory in early Friday trading.

Brent crude oil prices were down about six-tenths of a percent early Friday to $62.82 per barrel, 3.5 percent below the start of the month. West Texas Intermediate, the U.S. benchmark, lost eight-tenths of a percent to $59.20 per barrel, down 1.3 percent from June 1.

Crude oil prices are up about 25 percent since the start of the year, eating away at the dramatic plummet that began in June 2014 when oil prices were above $100 per barrel. The modest recovery is in response to signs of increased demand in an expanding global economy, though the pace of economic growth has been slow.

Greece, whose economic cloud hung over the global financial crisis, could default on its debt unless negotiators can reach an agreement before the end of the month. Deal makers meet again Saturday, though Mujtaba Rahman, a director at risk consultant Eurasia Group, told The New York Times any agreement could be "economically suboptimal."

The Bank of Greece earlier this month warned that a manageable debt crises could "snowball into an uncontrollable crisis" without some form of agreement.

In the United States, growth has been slow, but steady. Consumer spending is up and employment rates are at levels considered healthy.

The International Monetary Fund said the U.S. economy was showing forward momentum, but warned of "dark corners" where small-scale crises could have large-scale effects.