Members of the United Nations Security Council, including the United States, expect the Council to reject a US bill to extend the arms embargo on Iran next week.
This has pushed Washington to prepare alternatives in case its draft law is rejected.
This rejection could also spark a new diplomatic conflict between the members supporting the US bill and those opposing it, mainly Russia and China.
US Secretary of State Mike Pompeo announced on Wednesday that US President Donald Trump’s administration will put forward its long-awaited resolution despite ardent opposition from Russia and China.
UN diplomats said opposition to the resolution’s current form is so widespread that Washington is unlikely even to secure the nine votes required to pass it.
They affirmed that and Moscow and Beijing are also likely to veto it.
European allies of the US -- who along with Russia and China, signed the deal with Iran -- have voiced support for extending the conventional arms embargo but their priority is to preserve the Joint Comprehensive Plan of Action (JCPOA).
The US text, seen by AFP, effectively calls for an indefinite extension of the embargo on Iran. Diplomats fear the resolution threatens the nuclear agreement, while Iran says it has the right to self-defense and that a continuation of the ban would mean an end to the nuclear deal.
Experts say the gap between the US and its allies threatens a summer of discontent at the Security Council as the October 18 deadline approaches.
UN-watchers suggest that EU countries on the Council could be brought on-board by a short-term extension of the embargo if it helps preserve the nuclear deal.
Or members may propose their own draft resolution, but finding consensus is likely to be difficult with China and Russia intending to veto.
The US has threatened to try to force a return of UN sanctions if it is not extended by using a controversial technique called "snapback," which would restore all UN sanctions on Iran.
A push for snapback “seems very likely,” some said, noting that this could torpedo the nuclear deal once and for all, which may be what Pompeo wants.
Pompeo has offered the contested argument that the United States remains a “participant” in the nuclear accord as it was listed in the 2015 resolution -- and therefore can force a return to sanctions if it sees Iran as being in violation of its terms.
He pointed to Iranian support to Yemen’s Houthi rebels as an example of an arms violation and has expressed alarm at indications that China is already preparing arms sales to Iran upon the embargo's expiry.