It may take until June before there is support for such a move, and even then the measures adopted are likely to be less than the United States and European Union would like; but it should be sufficient to keep pressure on Tehran, he said.
"It really is a push to get big business out of Iran and a push to get China on board with the UN resolution, even if on board just means an abstention," said Matthew Levitt, a senior fellow at the Washington Institute and a former deputy assistant secretary for intelligence at the US Treasury.
"What will end up happening is China, Lebanon and Brazil will abstain," he said, but there will still be enough votes in the Security Council to pass the resolution and no veto.
Any package of sanctions is likely to focus on restricting the operations of Iranian banks and insurance companies, the Iranian state shipping company IRISL and a large engineering group linked to the Iranian Revolutionary Guard Corps, he said.
The United States, Britain, Germany and France are driving efforts for a fourth round of sanctions to slow Iran's uranium enrichment programme, which they say is aimed at developing nuclear weapons but Iran maintains is for peaceful purposes.
The US and EU had hoped to secure backing for a new UN resolution by February, but opposition from Russia and China - two permanent members of the Security Council with veto powers - made that impossible. Russia has since softened its stance, while China continues to indicate that it is opposed.
Levitt, whose work in government focused on stemming the flow of terrorism financing, said failure to impose further sanctions - whether via the UN or unilaterally by the EU and the United States and others - could aggravate tensions.
"The more we dither, the more we increase the likelihood of a military conflict," he said. "We sit on our thumbs and put business first with Iran at real cost." CREDIBLE THREAT The United States has tried to emphasize that any sanctions package should not unduly affect the Iranian people, instead focusing on senior members of the Revolutionary Guards and institutions linked to the nuclear programme.
Measures targeting Iran's energy sector - Iran is the world's fifth largest exporter of crude oil - are deemed off limits and are likely to be vetoed by China, which is one of the largest buyers of Iranian oil.
But Levitt said steps were being taken by Saudi Arabia and the United Arab Emirates to increase their oil supplies to China, effectively weaning it off Iranian supplies. That might increase the likelihood of China backing a resolution.
"The UAE and Saudis have already begun ramping up production, they are already producing more reliable, cheap, high-quality oil to China and are fully capable of completely filling in for what China otherwise gets from Iran," he said.
Even if more sanctions are approved by June, Levitt said they were unlikely to put a stop to Iran's nuclear ambitions. Further measures would likely still be necessary, and even then he said a small military confrontation with Iran might be the only way of convincing Tehran that the West meant business.
"There are people who believe that there would be utility in having some type of limited skirmish with Iran... so that the Iranians understand that we are serious," he said.
"There's a good reason to believe that they simply don't believe in deterrence anymore... If you want to rely on any level of deterrence, there has to be a credible threat."
