United Parcel Service Inc., a leading package carrier for online retailers, is taking a major step toward expanding its ability to deliver in international markets by acquiring Netherlands-based TNT Express N.V. for $6.77 billion (5.16 billion euros) in an all-cash deal, the two companies announced today.

UPS provides shipping services for 136 retailers in the Internet Retailer Top 500 Guide, 274 in the Internet Retailer Second 500 and six in the Internet Retailer Top 400 Europe. UPS delivers on average 15.8 million items per day to 200 countries and territories, and with TNT Express that will increase by some 1 million packages per day throughout Europe, the Middle East, Africa, Asia-Pacific and the Americas, UPS says.

UPS reported 2011 revenue of $53.11 billion, and says its annual revenue will increase to more than $60 billion with TNT Express. TNT reported 2011 revenue of $9.51 billion (7.25 billion euros).

In other developments in its international business, UPS also says it will invest $200 million to expand its transportation hub in Cologne, Germany.

In UPS’s annual report for the year ended Dec. 31, 2011, however, chairman and CEO D. Scott Davis said the company expected slow growth this year in Europe and Asia.

Morgan Stanley, UBS and Bank of America Merrill Lynch are acting as financial advisors to UPS in the acquisition; Goldman Sachs and Lazard B.V. are acting as financial advisors to TNT Express. Freshfields Bruckhaus Deringer is acting as legal counsel to UPS; Allen & Overy is acting as legal counsel to TNT Express.

The IRCE $200 early-bird discount expires Mar. 31.