* 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 (Adds stock market close, protesters disperse)
By Kanupriya Kapoor and Fransiska Nangoy
JAKARTA, Aug 21 (Reuters) - Indonesian police fired teargas 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.
Judges started reading through their findings - estimated to be hundreds of pages long - in the afternoon and it could take hours before a final verdict is announced.
The court is widely expected to uphold Joko Widodo's election victory and 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 gathered near the court and police fired teargas and water cannons to disperse protesters trying to break through security barriers shortly after the court began its session.
Witnesses said protesters rammed four trucks into the barriers, sparking the police response. A few people were injured and four were arrested. The crowds later largely dispersed.
About 50,000 police and military personnel are on standby around the capital in case of more violence, authorities said. Some businesses and schools closed early.
Political rallies in Jakarta have been peaceful since the hearing began two weeks ago.
A spokesman for Prabowo urged supporters to refrain from violence.
"We will respect the court's decision because it is final and binding," Tantowi Yahya told Reuters. "Prabowo has repeatedly said to his supporters to be calm and peaceful."
Indonesian stocks closed at a 15-month high, up 0.31 percent at 5,206.14 and near a record high. The rupiah also strengthened against the dollar.
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, which has been commended by international observers for its transparency, declared Widodo the winner by nearly 8.5 million votes, with more than 53 percent of the vote.
Prabowo's lawyers said there were mistakes at 52,000 polling stations and that their client, a former general, had won the election by about 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 upholds 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 Gayatri Suroyo, Fergus Jensen and Eveline Danubrata; Writing by Randy Fabi; Editing by Jeremy Laurence and Robert Birsel)