LOS ANGELES/DETROIT (Reuters) - McDonald's Corp reported a stronger-than-expected 4.8 percent rise in worldwide May sales at established restaurants, but said it expects a weak euro to take a bite out of full-year profits.

Roughly a quarter of McDonald's consolidated operating income originates in countries that use the euro currency, the world's biggest hamburger chain said yesterday.

Based on current exchange rates, McDonald's expects currency conversion to hurt full-year net income per share, versus its previous expectation for a slight benefit. The company, which gets more than half of its revenue and profits from outside the United States, gave no further details.

Yesterday, the euro hovered near a four-year low against the dollar on concerns over a widening European debt crisis that has struck financial markets and could constrict consumer demand. The currency fluctuations have been "wild and crazy" since McDonald's last gave currency guidance in April, Edward Jones analyst Jack Russo said.

He said the risks now are two-fold: Possible austerity measures around Europe could put a dent in consumer spending.