NEW YORK, June 23 (Reuters) -

The United Nations Security Council is due to hold a first round of talks on Wednesday on a U.S. proposal to indefinitely extend an arms embargo on Iran, which is currently set to end in October under Tehran's 2015 nuclear deal with world powers.

The United States circulated a draft resolution on the measure to the 15-member council on Monday, diplomats said, but council veto-powers Russia and China have already signaled their opposition to the move.

Washington has long argued that the arms embargo on Iran should not be lifted. A resolution needs nine votes in favor and no vetoes by the United States, China, Russia, Britain or France to pass.

The U.S. draft would ban the sale, supply or transfer of arms or related materiel by Iran and prohibits countries from selling, supplying or transferring arms or related materiel unless approved by a Security Council committee.

It requires countries to inspect cargo in their territory if they have reasonable grounds to believe the cargo contains banned items and also calls on countries to inspect vessels on the high seas - with the consent of the flag state - for the same reason.

The United States circulated the draft resolution after U.N. Secretary-General Antonio Guterres reported to the Security Council earlier this month that cruise missiles used in several attacks on oil facilities and an international airport in Saudi Arabia last year were of "Iranian origin."

If Washington is unsuccessful in extending the arms embargo, it has threatened to trigger at the Security Council a return of all U.N. sanctions on Iran under the nuclear deal, even though it quit the accord in 2018. Diplomats say Washington would face a tough, messy battle.

Iran has breached parts of the nuclear deal in response to the U.S. withdrawal and Washington's reimposition of sanctions.