VIENNA (Reuters) - Telekom Austria's (>> Telekom Austria AG) second-quarter core earnings fell by 10 percent, a slightly steeper fall than expected, as it spent more on subsidising smartphones to keep high-spending customers.

The company, in which Carlos Slim's America Movil (>> America Movil SAB de CV) owns almost 24 percent, reiterated on Monday it expected full-year revenues of 4.1 billion euros ($5.5 billion), down from 4.33 billion euros last year, but trimmed its investment plans.

Average revenue per user fell 15 percent in Austria to 16.2 euros per month following the integration of budget brand Yesss, which it acquired as a side deal to the takeover of Orange Austria by Hutchison Whampoa (>> Hutchison Whampoa Limited) at the start of the year.

Telekom Austria said Austria, Bulgaria and Croatia - its three biggest profit contributors and the markets in which it also has fixed-line operations, remained intensively competitive despite the consolidation in Austria.

"As expected, 2013 is turning out to be a mixed year," Chief Executive Hannes Ametsreiter said in a statement.

"Based on our convergent product portfolio and on higher subsidies for top smartphones in the premium customer segment, we are succeeding in securing our business. At the same time, our cost-cutting measures are partly compensating for the declines in revenues."

Second-quarter revenue fell 2 percent to 1.04 billion euros ($1.39 billion), in line with expectations, and comparable earnings before interest, tax, depreciation and amortisation (EBITDA) fell 10 percent to 330 million euros.

The EBITDA result was slightly below the average forecast in a Reuters poll.

Telekom Austria, Austria's biggest telecoms operator, said its capital expenditure would be 650-700 million euros this year, down from its previous forecast of around 700 million.

America Movil on Friday bid 7.2 billion euros for the rest of Dutch group KPN (>> KPN KON), sending shares in Telekom Austria higher on speculation Slim would bid as well for the other European operator in which he took a stake last year.

(Reporting by Georgina Prodhan; Editing by Michael Shields)