Spanish phone giant Telefonica SA (TEF) is losing ground in Colombia to its Mexican rivals, after investing 4.8 trillion Colombian pesos ($2.38 billion) between 2005 and 2009 in the Andean nation.

The Spanish company entered Colombia later than Mexico's America Movil SAB (AMX), its main mobile competitor, with the goal of gaining market share. Its expansion plans ran into technological problems, however, and some decisions didn't pay off as expected, analysts say.

The market share of Telefonica's local mobile phone unit fell to 22% at the end of June from 26% a year earlier, while that of America Movil unit Comcel SA rose to 68% from 64%, according to data from Colombian regulators.

Telefonica reported just under 144,000 pay-TV subscribers at the end of June, compared with more than 1.75 million served by the local unit of Telmex Internacional SAB (TII), which, like America Movil, is controlled by Mexican billionaire Carlos Slim.

"Telefonica and Slim are arch-enemies," said Martin Lara, an analyst with Mexican brokerage Vector. "In Colombia, Slim's people have had the upper hand."

Comcel reported a net profit of COP1.09 trillion in 2008, according to data from the regulator for non-financial companies, while Telefonica's mobile phone unit booked a net loss of COP268 billion. Telmex Internacional registered a profit of COP466 billion in 2008.

Telefonica had around 9 million mobile customers in Colombia at the end of June, about a third of what America Movil had.

Lara said size is important for a mobile telephone operator because of high fixed costs, which are roughly the same for 1 million lines or 10 million lines.

Jose Otero, a Buenos Aires-based telecom analyst with consultancy Signals Telecom, said the Spanish company lost customers when it switched to the GSM standard, which turned out to be much more complicated than expected in Colombia.

Also, Telefonica's strategy on pricing cell phone calls below America Movil didn't appear to pay off, and ended up reducing its average revenue per user, Otero added.

Telefonica officials declined to comment for this article.

Telefonica entered the Colombian market in 2005, when it bought the Latin American operations of U.S.-based mobile telephone operator Bellsouth Corp. Comcel bought a local operator in the late 1990S.

Telefonica failed to dent the supremacy of Comcel even though the market has grown fourfold since the end of 2004, to 40.82 million mobile phone lines in a country of 45 million people.

In 2006, Telefonica won the control of state-owned Colombia Telecom with an offer of about $370 million. Telefonica started to offer the bundling of Cable TV, broadband and fixed telephone lines, known as triple play.

But Telmex Internacional has been more successful in triple play, even though it missed the acquisition of Colombia Telecom in 2005 when the country's comptroller annulled an agreement reached between Telmex and the government.

Telmex didn't participate in the subsequent auction, but instead went on a shopping spree for cable TV operators. In a matter of months, Telmex bought six TV operators, garnering more than 55% of the Colombian market, and has kept on growing. Telmex spun off Telmex Internacional in 2008.

Otero of Signals Telecom said Telefonica has the financial strength to invest and improve its standing in Colombia.

In the coming months, the state-owned telephone company Empresa de Telecomunicaciones de Bogota (ETB.BO) will sell a controlling stake to a "strategic operator," and other Colombian operators such as Medellin-based UNE and Cali-based Emcali may follow suit. Telefonica would be a possible candidate, Otero said. The company's market shares in Colombia wouldn't raise any antitrust issues.

-By Inti Landauro, Dow Jones Newswires; 57-1-610 70 44 Ext. 1131; colombia@dowjones.com

(Diana Delgado contributed to this article).