UPS Inc. said today it will withdraw its proposed $6.8 billion acquisition of Dutch parcel firm TNT Express after the European Commission (EC) told the companies it would block the deal.

The deal ends UPS' 10-month quest to buy TNT Express, which is considered the leading parcel company in Europe. Almost from the start, European regulators voiced antitrust concerns over the deal. The companies submitted multiple proposals to allay regulators' fears, the most recent being on Nov. 30 when it proposed to sell assets and to allow rivals access to its air networks.

At the time, the EC, the European Union's regulatory body, extended its review period of the deal from mid-January to Feb. 5. Based on today's announcement, it didn't have to wait that long. No details were given on the EC's decision or its rationale behind it.

The EC will issue a formal ruling in the next several weeks, Atlanta-based UPS said in today's announcement.

"We are extremely disappointed with the EC's position," said UPS Chairman and CEO Scott Davis in a statement. "We proposed significant and tangible remedies designed to address the EC's concerns with the transaction. The combined company would have been transformative for the logistics industry, bringing meaningful benefits to consumers and customers around the world, while supporting growth in Europe in particular."

Davis didn't rule out future acquisitions of meaningful size. The TNT transaction would have been far and away UPS' most expensive acquisition in its 106-year history.

"While we viewed the acquisition as a compelling growth platform, our financial strength allows UPS to capture future opportunities," he said.

UPS said it will pay TNT Express a $267 million "breakup fee" for withdrawing the proposal.

Although market share estimates vary, it is believed that TNT controlled about 16 to 18 percent of the intra-European delivery market. UPS held approximately 10 percent to 14 percent of the segment. The transaction, if it went through in its original form, would have made UPS the leader in the European parcel market. No other company made a counteroffer for TNT Express.

With the UPS deal in tatters, financially troubled TNT Express now faces the prospects of either waiting for another suitor or competing on its own. In May 2011, the unit was spun off from the Dutch postal system amid rumors that the unit would eventually be put up for sale. TNT Express' stock price subsequently declined as a weak European economy and rising operating costs took their toll on the company's revenue and earnings.

TNT Express' stock climbed during a large part of 2012 as hopes increased that the UPS deal would come to fruition. In European trading today, however, the stock plunged nearly 40 percent from its close on Friday.