MILAN (Reuters) - A Milan court on Wednesday ordered an expert opinion on Silvio Berlusconi's health as the former Italian prime minister's trial on bribery charges has been repeatedly delayed due to his hospital visits.

       The trial began in 2017, with 84-year old Berlusconi charged with bribing witnesses in a previous case where he was accused of paying for sex with a minor, in which he was finally acquitted. He has pleaded not guilty.

       Berlusconi, who served four terms as prime minister, has been in and out of hospital this year after contracting COVID-19 last September and speculation has mounted over a serious deterioration of his health. He has been hospitalised twice in the last two weeks.

       On Tuesday Berlusconi's lawyer filed a motion to suspend the trial due to his client's heart problems and generally fragile condition. The prosecutor's office opposed the request.

       The leading judge in the case, Marco Tremolada, said on Wednesday the matter would be resolved by the judgement of a medical expert to be appointed at a hearing on Sept. 15.

       "The court's decision is balanced and fair", Berlusconi's lawyer Federico Cecconi told reporters after the ruling.

       Berlusconi's last government collapsed in 2011 amid a debt crisis and scandal over his notorious "bunga bunga" sex parties attended by models and a teenage girl nicknamed Ruby.

       Those parties gave rise to the original "Ruby" trial at which he was acquitted in 2015.

       Berlusconi has also been tried for numerous alleged financial crimes, and was found guilty of tax fraud in 2013, his only definitive conviction.

       His Forza Italia party has lost most of its former support, but remains a significant player on Italy's fragmented political scene.

       (Reporting by Emilio Parodi, editing by Gavin Jones and Angus MacSwan)