UPDATE 1-Bwin earnings beat forecast, customer numbers down

(Adds customer numbers, detail, background)

VIENNA, May 15 (Reuters) - Austrian Internet betting and gambling operator bwin Interactive Entertainment (BWIN.VI) posted a 57-percent rise in first-quarter core earnings on Tuesday, but said marketing cuts would weigh on client numbers.

Earnings before interest, tax, depreciation and amortisation (EBITDA) came in at 23.2 million euros ($31.4 million) as bwin cut marketing expenses by 40 percent, beating the average EBITDA forecast of 16.6 million in a Reuters poll of four analysts.

The cuts in marketing expenses, set to continue over the course of the year if bwin makes good on its pledge to reduce them by half, led to a decrease in both active and new customers over the quarter to March, and bwin said this trend would continue.

"The decline in new active customers and less effective churn management by comparison were attributable mainly to a drastic reduction in the marketing budget," bwin said in a statement.

"In the short term, the company could therefore face weaknesses in the activation of customers and less dynamic growth of new customers," it said.

Bwin last year promised to halve marketing costs -- which include shirt sponsorship for soccer teams Werder Bremen and AC Milan -- after a U.S. crackdown on Internet gambling forced it to write off half a billion euros of online poker assets.

Bwin shares have been on a roller-coaster ride since they hit an all-time high of 105.50 euros last May. At the lowest level, they changed hands at 13 euros in November before rising again to Monday's closing price of 33 euros.

Bwin made no comment on its talks to take over British rival Sportingbet (SBT.L) in its statement.