Russian Ambassador Vassily Nebenzia said it was unclear whether missiles and weaponry used by the rebels were Iranian-made or whether they were shipped before the arms embargo on Yemen was imposed in 2015, casting doubt over the findings of a UN panel of experts.

"Iran is vehemently denying it is supplying anything to Yemen," Nebenzia told two reporters.

"Yemen hosts a pile of weapons from the old days. Many countries were competing to supply weapons to Yemen during the time of president Saleh, so I cannot give you anything conclusive," he said.

Ali Abdullah Saleh was Yemen's leader 1990-2012. He was killed in December by his erstwhile Huthi rebel allies.

Asked whether the case had been made for action against Iran, the ambassador answered "no."

Nebenzia joined UN Security Council ambassadors on a visit to Washington this week to inspect debris from missiles that the United States says were supplied by Iran to the Huthis.

The ambassadors had lunch with President Donald Trump, who urged the council to take steps to counter "Iran's destabilizing activities" in the Middle East.

A recent report by the panel of experts bolstered the US claims when it concluded that Iran had violated the arms embargo on Yemen by failing to block supplies of missiles to the rebels.

The Trump administration has said it will seek action at the Security Council against Iran, although it has yet to specify what those measures might be.

"If there is something we will see. How can we pass judgment prematurely before we know what it is about," Nebenzia said.

Russia has the power to block sanctions by resorting to its veto power as one of the five permanent Security Council members along with Britain, France, China and the United States.

US Ambassador Nikki Haley last month presented the missile fragments as "undeniable" evidence that a ballistic missile fired by Yemen's Huthi rebels at Saudi Arabia in November was Iranian-made.