United Parcel Service , the world's largest package delivery service, on Tuesday reported higher first-quarter earnings, reflecting an improving global economy and higher international volume.

UPS posted a profit of $533 million, or 53 cents per share, compared with $401 million, or 40 cents per share, a year earlier, in line with its April 14 preannouncement of the quarter's numbers, but its shares lost about 1 percent in early trading.

Stripping out special items, UPS's adjusted earnings of 71 cents per share beat average analyst estimates of 57 cents per share, according to Thomson Reuters I/B/E/S.

With global economies showing signs of recovery and UPS's strong start to 2010, we are optimistic about this year and the future, UPS Chief Executive Officer Scott Davis said in a statement.

Revenue rose 7 percent to $11.7 billion.

The International Package segment posted an 18 percent jump in revenue as average daily volume increased 18 percent, while average daily volume rose in the domestic package segment as well, the first year-over-year growth in two years.

Atlanta-based UPS also confirmed its 2010 outlook, which it raised on April 14 to a range of $3.05 to $3.30 per share. The outlook's midpoint of $3.18 beat analyst estimates of $3.16.

Both UPS and rival FedEx Corp are considered to be bellwethers because an increase in their volumes correlates with economic strength.

The companies' shares have rallied so far this year as the broader economy has strengthened, with UPS's shares up about 18 percent, not far off their 52-week high of $69.74, and FedEx's up about 11 percent.

UPS shares were down about 1 percent, or 70 cents, at $67.80 in early New York Stock Exchange trading.

The stock is up 6 percent since the mid-April earnings preannouncement.

(Reporting by Helen Chernikoff; Editing by Lisa Von Ahn and Maureen Bavdek)