UNITED NATIONS (Reuters) - The United Nations Security Council is due to vote on Wednesday on a bid for an international tribunal to prosecute those suspected of downing a passenger airliner last year in Ukraine, but Russia said on Friday it was likely to block the move.

Malaysia last month circulated a draft resolution to form the tribunal. Russia last week proposed a rival text that demands justice for the victims of Malaysia Airlines flight MH17, but does not establish a tribunal.

Flight MH17 was shot down in July 2014 with 298 passengers on board, two-thirds of them Dutch. It crashed in Ukrainian territory held by Russian-backed separatists.

The vote on the proposal by Malaysia, Australia, the Netherlands and Ukraine to create an international tribunal is set for Wednesday afternoon, according to New Zealand, president of the U.N. Security Council for July.

"Malaysia did include some language from our draft in their draft text but it did not go to the core of our concern, they kept insisting on the need to establish right now an international criminal court," Russian U.N. Ambassador Vitaly Churkin told Reuters on Friday.

"This is not a proper thing for the Security Council to do because it's not a case of a threat to international peace and security," Churkin said in a phone interview.

Ukraine and Western countries accuse the rebels in eastern Ukraine of shooting down the plane with a Russian-made missile. But Moscow has rejected accusations it supplied the rebels with SA-11 Buk anti-aircraft missile systems.

Churkin said that while he had not received definitive instructions from Moscow on how to vote on Wednesday, he said: "I have a very strong feeling that it's not going to lead to a result that will be satisfactory for the Security Council."

"We are against it," Churkin said. Russia is a Security Council veto power, along with the United States, Britain, France and China.

Several council diplomats, speaking on condition of anonymity, said they expected Russia to veto the resolution.

Foreign ministers for Malaysia, Australia, the Netherlands, Belgium and Ukraine are expected to attend the planned vote on Wednesday, diplomats said.

Led by the Dutch, those countries are conducting a criminal inquiry in the downing of MH17. Separately, a final report on the cause of the crash is due in October from the Dutch Safety Board.

On July 21, 2014, the Security Council unanimously adopted a resolution that demanded that those responsible "be held to account and that all states cooperate fully with efforts to establish accountability."

(Reporting by Michelle Nichols; Editing by James Dalgleish and Andrew Hay)