The UN Security Council is preparing to vote this week on a US proposal to extend an arms embargo on Iran, a move that some diplomats say is bound to fail and put an already fragile nuclear deal between Tehran and world powers further at risk.
WHY IS THE ARMS EMBARGO ON IRAN EXPIRING?
The United Nations Security Council imposed an arms embargo on Iran in 2007.
The embargo is due to expire in mid-October, as agreed under the 2015 nuclear deal among Iran, Russia, China, Germany, Britain, France and the United States that prevents Tehran from developing nuclear weapons in return for sanctions relief. That accord is enshrined in a 2015 Security Council resolution.
In 2018, US President Donald Trump quit the accord reached by the Obama administration, dubbing it "the worst deal ever."
WHY DOES THE UNITED STATES WANT TO EXTEND THE ARMS EMBARGO?
The Trump administration has been particularly hawkish toward Iran and accuses the Islamic Republic of being a state sponsor of terrorism and meddling in conflicts throughout the Middle East, including Yemen and Syria, and beyond.
US Secretary of State Mike Pompeo said in June that if the embargo is lifted, "Iran will be free to become a rogue weapons dealer, supplying arms to fuel conflicts from Venezuela, to Syria, to the far reaches of Afghanistan."
Iran has denied the US accusations.
WHY ARE RUSSIA AND CHINA OPPOSED TO EXTENDING THE ARMS EMBARGO?
Iran allies Russia and China argue that Washington has no legal basis for pushing the Security Council to extend the embargo. They say that the 2015 council resolution enshrining the nuclear deal - and the arms embargo and its expiration - should be implemented.
Russian Foreign Minister Sergey Lavrov said in May: "The United States must recognize that there are neither legal nor other grounds for its policy of using Security Council mandates to pursue its own selfish interests."
Washington says Russia and China want to sell weapons to Iran when the embargo expires.
WHAT DOES THIS MEAN FOR THE 2015 NUCLEAR DEAL?
Even though the United States has withdrawn from the nuclear deal, Washington has threatened to use a provision in the agreement to trigger a return of all UN sanctions on Iran if the Security Council does not extend the arms embargo.
While diplomats predict the so-called sanctions snapback process at the UN Security Council would be messy - with the remaining parties to the nuclear deal opposed to such a move - it could ultimately kill the nuclear deal because Iran would lose a major incentive for limiting its nuclear activities.
Since Washington quit the deal it has imposed strong unilateral sanctions and in response Iran has breached parts of the nuclear deal.
Iran's Foreign Minister Mohammad Javad Zarif on Tuesday described the next few weeks and months as "critical."
"I am confident that ... members of the Security Council will refute the campaign struggle of a beleaguered US administration to turn what was the diplomatic achievement of the 21st century into an exercise in futility," he said, referring to the November US presidential election.
WHAT SANCTIONS WOULD SNAP BACK?
A snapback of UN sanctions would require Iran to suspend all nuclear enrichment-related and reprocessing activities, including research and development, and ban imports of anything that could contribute to those activities or to the development of nuclear weapon delivery systems.
It would reimpose the arms embargo, ban Iran from developing ballistic missiles capable of delivering nuclear weapons and reimpose targeted sanctions on dozens of individuals and entities. States would also be urged to inspect shipments to and from Iran and authorized to seize any banned cargo.