By Anthony Deutsch
ROTTERDAM (Reuters) - The Dutch prosecutor leading the investigation into the downing of Malaysia Airlines flight MH17 over Ukraine last year said on Tuesday he was confident of concluding his investigation successfully but was not yet ready to issue arrest warrants.
The plane with 298 passengers on board, two-thirds of them Dutch, was shot down in July and crashed in territory held by Russian-backed separatists in eastern Ukraine.
"We are not yet far enough that we have formal suspects identified or are ready to arrest suspects," said Fred Westerbeke, leading the international investigation.
He said based on the pace of the inquiry and the evidence gathered so far he was "confident" that suspects would eventually be brought before a judge.
The Netherlands is discussing with its allies the option of establishing an international tribunal to prosecute suspects, sources have told Reuters, possibly under the auspices of the United Nations.
Westerbeke said a tribunal may be the best option because it would have widespread, international backing.
Prosecutors believe the plane was likely shot down by a ground-to-air missile, but Westerbeke said he could not yet rule out other theories.
Moscow says the passenger jet was hit by a rocket fired from a Ukrainian fighter jet. Kiev denies that.
After reviewing vast quantities of data, social media postings, video evidence and interviewing 100 witnesses, Westerbeke said: "A large group of people have been identified as persons of interest."
Investigators from the Netherlands, Belgium, Malaysia, Australia and Ukraine will need until the end of 2015 and possibly longer, to conclude their case, he said.