Deutsche Telekom Q1 core profit up 12.9 pct helped by U.S.

* Q1 adj EBITDA 5.16 bln euros vs 5.14 bln avg expected

* Investments weighs, free cash flow down 5 pct

* Still sees 2016 adj EBITDA of around 21.2 bln euros (Adds details about U.S (Other OTC: UBGXF - news) ., background)

FRANKFURT, May 4 (Reuters) - Deutsche Telekom (LSE: 0MPH.L - news) said on Wednesday its first-quarter core profit rose on the back of its ongoing success in the United States, which offset investments in its European networks.

The company said adjusted earnings before interest, tax, depreciation and amortisation (EBITDA), excluding special items, rose 12.9 percent to 5.16 billion euros ($5.93 billion), slightly ahead of the average estimate of 5.14 billion euros in a Reuters poll.

Last week T-Mobile US Inc reported a net profit for its fiscal second quarter and raised its 2016 forecast for customer additions.

Contributing 7.82 billion euros to Deutsche Telekom's revenues, T-Mobile US is Deutsche Telekom's biggest unit.

In Europe and Germany, Deutsche Telekom is heavily investing in upgrading its fixed networks.

Investments rose 11.9 percent to 2.8 billion euros in the first quarter, weighing on free cash flow, which dropped 5 percent to a lower-than-expected 822 million euros.

Deutsche Telekom said it still expected 2016 adjusted EBITDA to rise to around 21 billion euros and free cash flow of around 4.9 billion.

($1 = 0.8708 euros) (Reporting by Harro ten Wolde; Editing by Maria Sheahan)