Malaysia is expected to present a draft resolution to the Security Council next month on setting up the tribunal, said the diplomat, who asked not to be named.
"They are looking for agreement to establish a UN tribunal that would be the way to hold accountable," he said.
It remains unclear, however, whether Russia would back the creation of the special tribunal, modelled after other courts set up by the United Nations for the prosecution of serious crimes.
Suspicions immediately turned to the pro-Russian separatists in east Ukraine who may have used a surface-to-air missile supplied by Russia to shoot down the plane.
Spurred by a global outcry over the downing, the Security Council last year adopted a resolution demanding that the perpetrators be brought to justice.
The five countries of the Joint Investigation Team -- Australia, Belgium, Malaysia, the Netherlands and Ukraine -- met last week in New York to discuss the proposed international court.
Malaysia is hoping that the council will adopt the measure on July 22 to mark the one-year anniversary of the first resolution passed just days after the tragedy.
There is also concern that the resolution should be adopted before the criminal investigation is completed in the coming months, the diplomat said.
The Netherlands has been tasked with leading the investigation into the cause of the accident and identifying the victims.
