NEW YORK (TheStreet) -- Stocks hit new session lows in the final hour of trading Monday as Wall Street's focus returned to fears over a Greek exit from the eurozone. Over the weekend, Greek Prime Minister Alexis Tsipras reiterated his commitment to rolling back austerity measures.

The S&P 500 was down 0.61% and the Nasdaq fell 0.47%.

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Though U.S. markets reacted negatively, economists agree that for the most part the actual impact on Wall Street would be negligible.

"How the Greek situation plays out just adds to that worry overall," said David O'Malley, CEO of Penn Mutual Asset Management, in a call. "But if that remote possibility comes through and they do leave the eurozone area, I think it has virtually no impact on the global economy."

In a press conference midday, President Barack Obama and German Chancellor Angela Merkel pledged to do all they could to restore peace in the Ukraine and bring economic stability to Greece. Obama said he was looking to Merkel's appraisal of the Greek situation and would support the country's approach to restoring stability in the eurozone. Greek Finance Minister Yanis Varoufakis has been meeting with ECB officials to try to relax the conditions of the country's bailout package. 

The Dow Jones Industrial Average was 0.74% lower, dragged down by shares of McDonald's (MCD) . The world's largest fast food chain reported worldwide same-store sales tumbled 1.8% in January, a drop steeper than the expected 1.2% decline. Sales at U.S. restaurants rose just 0.4%. Shares fell 1.2%.

Crude oil moved higher after OPEC projected better-than-expected demand for crude this year. West Texas Intermediate crude rose 2.5% to $52.97 a barrel. The cartel said it expects demand for its oil at an average 29.21 million barrels per day, 430,000 higher than a previous forecast. Oil experienced a surge last week after U.S. rigs fell to their lowest since December 2011 and a number of oil giants announced plans to slash capex spending.

Oil companies such as Halliburton (HAL) , Chevron (CVX) , and Schlumberger (SLB)  were all higher, while the Energy Select Sector SPDR ETF (XLE) added 0.2%. 

HSBC (HSBC) fell 1.8% after admitting to failings at its Swiss arm, which allowed some clients to avoid taxes and conceal assets. The bank said its 1999 purchase of the subsidiary had yet to be fully integrated with central operations, leading to lower levels of compliance.

Hasbro (HAS) shares were up 7.1% after the toy maker beat earnings estimates for its fourth quarter amid a 21% jump in sales of boys toys, its highest-selling product category.

Alibaba (BABA) was edging higher on news the Chinese e-commerce company had paid $590 million for a stake in Meizu, a maker of low-end handsets.

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--Written by Keris Alison Lahiff in New York.