Global sales at established McDonald's (NYSE:MCD) restaurants rose by 2.6 percent in May, led by a 2.4 percent sales increase in the U.S. and a 2 percent sales boost in Europe.

In the U.S., breakfast and chicken options fared best on the menu for customers, driving the increase there, according to a company statement.

The U.K. hosted most of Europe’s McDonald’s fans, while German and French customers were less keen, dragging down potential sales.

Sales in Asia, the Middle East and Africa were up only 0.9 percent in May. The company cited flat sales in Japan and weakening sales in China, which has faced recent fears over Avian influenza.

The company cited the introduction of a new Egg White Delight sandwich and Premium McWraps as examples of its diversifying food menu.

The fast-food chain has fought to keep sales up as customers change their eating habits and the restaurant industry faces sluggish growth, according to the Associated Press.

Meanwhile, fast-food rivals like Burger King Worldwide Inc (NYSE:BKW), The Wendy’s Co (NASDAQ:WEN) and Subway have all fought to offer the cheapest deals to customers, in a bid to grow market share.

In late 2012, according to the AP, McDonalds reported a decline in monthly sales for the first time in almost 10 years. Since then, they’ve reported sales declines in January, February and April 2013.

April saw a 0.6 percent decrease in global sales.

Still, in the first three months of 2013, the company reported revenues of $6.6 billion, up 1 percent from 2012. It returned $1.1 billion to shareholders through dividends and share repurchases.

McDonald’s second-quarter results are expected around July 22, 2013. The franchise operates more than 34,500 outlets worldwide, in over 100 countries and for more than 69 million customers, according to its website.