UN diplomats said opposition to the resolution is so widespread that the US is unlikely to secure the nine votes required at the 15-member Security Council to force Russia and China to use their vetoes.
"The resolution takes a maximalist position on Iran," one diplomat told AFP. Another said the draft "goes beyond the current provisions" of the ban on conventional weapons sales to Iran.
The embargo will expire on October 18 under UNSC Resolution 2231, which enshrined the 2015 nuclear deal — officially known as the Joint Comprehensive Plan of Action (JCPOA).
However, Washington which unilaterally withdrew from the JCPOA in May 2018, seeks to keep the ban in place through a resolution.
"This is a car crash that everyone knows is going to happen," New York-based UN expert Richard Gowan said, describing the US draft as a "poison pill of a text."
"The focus should remain on preserving the JCPOA," a third diplomat stressed.
Secretary of State Mike Pompeo announced on Wednesday that the US would put forward its anti-Iran resolution despite ardent opposition from Russia and China.
Reports said the US text effectively calls for an indefinite extension of the arms embargo on Islamic Republic and uses hawkish rhetoric.
In an article, titled “Document of the Week: US Pushes Doomed Iran Resolution at UN” and published on Friday, the Foreign Policy magazine predicted that US President Donald Trump’s Iran gambit “has little chance of success.”
The draft resolution “is a classic piece of Trumpian diplomacy. It is bold, aiming to impose sweeping legal obligations on countries to confront and seize vessels carrying Iranian cargo. It is punitive, looking to subject multiple Iranian individuals and entities, including the Islamic Revolution Guards Corps, to an asset freeze and travel ban. And it is expected to secure little, if any, support from key Europeans allies, who feel the initiative would undercut the terms of the landmark 2015 Iran nuclear deal,” the article said.
Citing UN-based diplomats, it noted that Washington is expected to formally table the resolution on Monday, with plans to put it to a vote on Tuesday.
“China and Russia have made clear they would veto the US resolution. But they may not have to. Washington lacks the minimum nine votes it needs for a resolution to be adopted in the Security Council,” it added.
US Special Representative for Iran Brian Hook, who resigned this week, had asserted during his tenure that if the US resolution failed, the administration would pursue another approach to preserving the Iran arms ban.