It's official: the Subway sandwich chain has surpassed McDonald's Corp. as the world's largest restaurant chain, in terms of units.

At the end of last year, Subway had 33,749 restaurants worldwide, compared to McDonald's 32,737. The burger giant disclosed its year-end store count in a Securities and Exchange Commission filing late last month.

The race for global dominance is an important one for an industry that's mostly saturated in the U.S. High unemployment and economic uncertainty have battered the restaurant industry in the U.S., and chains are increasingly looking overseas for growth, particularly in Asia.

Starbucks Corp. recently said it plans to triple its number of outlets in China, for example. Dunkin' Brands Inc., parent of Dunkin' Donuts and Baskin-Robbins, plans to open thousands of new outlets in China in coming years as well as its first stores in Vietnam in the next 18 months. Subway just opened its 1,000th location in Asia, including its first in Vietnam.