UPDATE 1-Endesa confirms investments, silent on dividend

* Reiterates to invest 13.5 bln euro to 2013

* Endesa sees tariff shortfall paid off this yr

* Expects shortfall-related revenue before yr-end

* Endesa shares down 1.71 pct

(Adds reiteration on investment plan, details, share price)

MADRID, June 30 (Reuters) - Enel's ENEI.MC Spanish unit, Endesa (ELE.MC), reassured investors over its investment plan on Tuesday, but was silent over whether it would use gains from asset sales to boost its dividend.

Endesa is maintaining its investment target of 13.5 billion euros until 2013 and 800 million euros of synergies to 2012, in spite of the difficult economic environment, Chairman Borja Prado told shareholders at the company's annual meeting.

"We have a solid strategic plan which is adapted to the current situation and aimed at pushing the company forward," he said.

Prado did not make any reference to the 1.2 billion euros net capital gains booked from the sale of renewable and hydro assets to builder and energy company Acciona (ANA.MC) in Spain and Portugal.

Analysts had flagged that Enel might decide to use the funds to award a special dividend, which would help the Italian company toward its target of cutting debt to 45 billion euros in 2010 from 50.8 billion at the end of March, one of the highest in the sector.

At 1323 GMT, Endesa stock was down 1.71 percent, underperforming a 0.17 percent rise in the Dow Jones European Utility Index.

TARIFF SHORTFALL PAID IN 2009

Endesa expects its debt to be reduced by over 5 billion euros in 2009 when Spain pays power utilities the difference between fixed electricity tariffs and the cost of generating power, widely known as the tariff deficit.

"Endesa expects to obtain the revenues related to the tariff deficit before the end of the year," the chairman said, replying to a question during today's shareholders meeting.

Prado was making his first appearance as chairman of Endesa since Italian power firm Enel ENEL.MC acquired Acciona's stake in a cash and assets deal, boosting its stake in the Spanish utility to 92 percent.

(Reporting by Clara Vilar, writing by Sarah Morris, Judy MacInnes and Jonathan Gleave; editing by Simon Jessop)