President Obama downplayed the effects of a debt default by Greece, saying that the problem was "primarily of concern to Europe" just hours before the nation was expected to miss a payment on a loan from the International Monetary Fund.

"This is not something that we believe will have a major shock" on the U.S., the president said in a press conference at the White House Tuesday afternoon.

Acknowledging the seriousness of the possible default for the Greek people and for European growth, Obama said he has been involved in talks with his European counterparts and that Treasury Secretary Jack Lew has been "on the phone" with financial authorities to encourage negotiations.

Nevertheless, the president downplayed the potential fallout for the U.S. from a Greek default, suggesting that financial markets had already priced in negative outcomes.

Greece was facing a deadline Tuesday at midnight for a payment of the rough equivalent of $1.8 billion to the IMF.

U.S. stock markets were up slightly on the day through the early afternoon. Global stocks were relatively calm Tuesday after big drops on Monday.

Financial authorities in the U.S. have consistently sought to reassure the public that the country faces little threat from turmoil in Greece, which has been under stress since the financial crisis.

Nevertheless, Obama acknowledged that a Greek default and its repercussions for the euro zone could slow European growth, and in turn slow trade with the U.S.

"It's something that we take seriously but it's not something that I think should prompt overreactions," Obama said.