Updates with EMMA Capital's comment in paragraph 5, share price paragraph 7

June 25 (Reuters) - Ladbrokes-owner Entain ENT.L said on Thursday it had agreed to sell a 20% stake in its Central and Eastern Europe business to partner EMMA Capital for €425 million ($483 million), marking the first step in a phased exit aimed at reducing debt.

The company had begun exploring options for its joint venture in the region, including a potential sale, Reuters reported last week, citing three people familiar with the matter.

Entain, which operates BetMGM in the U.S. along with MGM Resorts MGM.N and Ladbrokes in the UK, has been under pressure to reduce costs to offset the impact of higher online gambling taxes in Britain though it has benefited from a shift toward online betting and gaming.

The disposal will lower Entain's stake to 47.5% from 67.5% and raise EMMA Capital's stake in Entain CEE to 42.5% while a voting agreement also gives the Czech investment firm sway over the Juroszek family's 10% interest.

Increasing the stake to become the largest voting shareholder was a completely logical next step, said Pavel Horák, Investment Director at EMMA Capital in a statement.

Entain said it would keep evaluating options to exit its remaining stake in the business, which owns SuperSport in Croatia and STS in Poland. The business generated £183.7 million ($242.25 million) EBITDA last year.

Shares in the Isle of Man-based Entain rose as much as 4% to 576.6 pence by 1350 GMT.

The company also updated guidance as the CEE business would no longer be fully consolidated. It now expects the annual core profit margin for its online division to be in the range of 21% to 22%, down from 23% to 24%, and said it was comfortable with market expectations for group core profit around £1.13 billion.

($1 = €0.8821)

($1 = £0.7583 )