TOKYO (Reuters) - Japanese business confidence among manufacturers improved for the first time in two quarters in the three months to September, a central bank survey showed, an encouraging sign that parts of the economy are stabilising.

However, sentiment for the services sector worsened more than expected, suggesting some companies are still struggling to shake off the impact of a sales tax hike in April.

The mixed data may do little to relieve pressure on policymakers to expand fiscal and monetary stimulus if the economy stumbles ahead of premier Shinzo Abe's crucial decision by year-end on whether to proceed with a second sales tax hike in October 2015.

The headline index for big manufacturers' sentiment improved by 1 point from three months earlier to plus 13 in September, the BOJ's closely-watched quarterly " tankan" survey showed on Wednesday. That compared with a median market forecast of plus 10.

However, the mood among big service-sector firms worsened by 6 points to plus 13 in September, the survey showed, as the sales tax hike in April hit consumption. The median market forecast was for a reading of plus 17.