Picture taken on Tuesday shows a test firing of an Iranian Nour missile from the Islamic republic's first domestically-manufactured destroyer, named Jamaran, off the southern shores of the Gulf. This is the first time a Nour missile is launched from the locally-made warship. Photo: AFP

Western powers face an uphill battle in their bid to forge consensus in the UN Security Council for new, tougher sanctions to force Iran to scale back its nuclear ambitions, diplomats say.

Israel's UN Ambassador Gabriela Shalev said Tuesday that prospects were poor for adoption by the 15-member council of "crippling" punitive measures against Iran.

"The chances now seem grim regarding sanctions that will be crippling," Shalev told reporters here, in large part because veto-wielding council members Russia and China, appear reluctant to back a new round of tough sanctions proposed by Washington and its Western allies.

"The Chinese and the Russians still hope that diplomacy will work. They do not want to inflict any harm on the Iranian people," she added.

Adoption of a resolution requires at least nine votes from the council and no veto from its five permanent members: Britain, China, France, Russia and the United States.

Western proponents of sanctions say ideally they would like to get unanimous council support to show that the world is united in the nuclear standoff with Tehran.

US Defence Secretary Robert Gates was keeping up the pressure on Iran, consulting with the United States' closest and most influential ally in the Persian Gulf about how to respond to Iran's disputed nuclear programme.

US officials said Weednesday Gates would discuss shared concerns over Iran's nuclear intentions and ballistic missile program during meetings with Saudi King Abdullah and senior leaders.