Dutch investigators have urged Russian government to hand over the radar data which shows that a Ukrainian jet was flying close to Malaysian Airlines flight MH17 when it was downed.
According to the BBC, Dutch chief investigator Fred Westerbeke said that his team was preparing a request for assistance.
Russia had claimed that a Ukrainian fighter jet shot down flight MH17 on July 17.
Ukraine and western countries have been blaming pro-Russian separatists in eastern Ukraine who are allegedly back by Russia. They also claim that the plane was downed by a Russian BUK surface-to-air missile.
The investigation in to the crash has also been hampered due to clashes between pro-Russian separatists and Ukrainian forces in eastern Ukraine.