* Widodo expected to get 'green light' as president
* Prabowo says July vote was tainted by mass fraud
* Protesters ram trucks into barriers, some people hurt
* Reforms held up by court challenge (Updates with protests, tear gas, start of verdict reading)
By Gayatri Suroyo and Fergus Jensen
JAKARTA, Aug 21 (Reuters) - Indonesian police fired tear gas to disperse thousands of protesters outside the country's top court in Jakarta on Thursday, as judges started delivering their verdict into last month's disputed presidential election.
Losing candidate Prabowo Subianto has asked the Constitutional Court to overturn the election result, saying the vote in the world's third largest democracy was tainted by mass fraud.
At around 2:30 p.m. (0730 GMT), judges started reading through their findings - estimated to be hundreds of pages long - and it could take hours before a final verdict is announced.
The country's highest court is widely expected to uphold Joko Widodo's victory from the ballot last month. The verdict cannot be appealed.
The case is widely seen as a face-saving gesture and has been a common course of action in previous elections. The court has never overturned the result of a presidential election.
Thousands of Prabowo supporters protested near the court on Thursday. Police briefly fired tear gas and water canons to disperse protesters trying to break through security barriers shortly after the court started session.
Witnesses said protesters rammed four trucks into the barriers, sparking the police response. A number of people were injured.
Around 50,000 police and military personnel are on standby around the capital city in case of more violence, authorities said. Some businesses and schools closed early as a precaution.
Political rallies in Jakarta have remained peaceful since the hearing began two weeks ago.
Uncertainty over the election has delayed at least one major economic reform policy, as the outgoing government awaits the verdict before launching talks with Widodo's transition team on how to address ballooning fuel subsidy costs.
"We are waiting for the Constitutional Court decision before starting discussions with the transition team," chief economics minister Chairul Tanjung told reporters on Wednesday.
The Elections Commission (KPU), which has been commended by international observers for its transparency, declared Widodo the winner by nearly 8.5 million votes, or more than 53 percent of the vote.
Prabowo's lawyers said there were mistakes at 52,000 polling stations and that the former general had actually won the election by around 1 million votes.
The case is seen as a major test for the Constitutional Court after the former chief justice was jailed for life in June for accepting bribes over local election disputes. Analysts say the court is keen to regain its reputation for independence.
If the court decides to uphold the election, Widodo will be able to speed up his preparations ahead of taking office on Oct. 20. He is expected to soon resign as Jakarta governor to focus on the transition.
A senior member of Widodo's transition team told Reuters, "We will be more open in discussing with the current government a possibility of raising fuel prices (before October)." (Additional reporting by Kanupriya Kapoor and Fransiska Nangoy; Writing by Randy Fabi; Editing by Jeremy Laurence)