The Greek default on debt to the International Monetary Fund in a market mindful of the causes of the global financial crisis sent oil prices lower Wednesday.

Brent crude oil prices started the first full trading day of July at $63.02 per barrel, about nine tenths of a percent below Tuesday's close. West Texas Intermediate, the U.S. benchmark, was down 1.3 percent from the previous session to $59.47 per barrel.

Crude oil prices are up about $20 per barrel from the start of the year amid signs global economic recovery was taking up some of the oversupply that pushed oil into a bear market in mid-2014. Prices are holding steady, however, amid concerns that any overall growth is lackluster.

Greece missed its June 30 $1.78 billion payment to the International Monetary Fund, defaulting on its debt, after failing to break an impasse with its European creditors. Though the default is reminiscent of the Greek issues that overshadowed the global financial crisis, most parties to the negotiations downplayed the severity of the consequences of missing payment to the IMF.

"Many developments so far confirm that the important steps that have been taken over recent years have made our Economic and Monetary Union more stable and more resilient," European Commissioner for the Euro and Social Dialogue Valdis Dombrovskis said Wednesday. "Whatever course events in Greece will take, I am convinced that EMU will be able to weather them."

Tuesday's deadline to reach a formal nuclear deal with Iran was extended as parties to the talks work to hammer out remaining issues. Iran already committed to scaling back its nuclear program in exchange for relief from sanctions, though Tehran has expressed reservations about verification details in the final package.

Yukiya Amano, general director of the International Atomic Energy Agency, met Wednesday in Tehran with Iranian President Hassan Rouhani to discuss outstanding issues.

A deputy petroleum minister in Iran said he expected a "great leap" in foreign oil investments in the post-sanctions climate.

Iran's export potential is limited by half under the terms of existing sanctions.