Vassily Nebenzia’s comments at a video news conference made clear that the administration of Donald Trump will have a tough time advancing any measures to impose further bans on Iran in the UN Security Council, where Russia has veto power.

The United States circulated a draft UN resolution that would indefinitely extend the UN arms embargo on Iran, which expires in October, to a small number of council members in late April.

It would strike the expiration of the arms embargo from the council resolution that endorsed the 2015 nuclear deal between six major powers – the US, Russia, China, Britain, France and Germany – and Iran, according to Trump administration officials and UN diplomats.

Nebenzia said the arms embargo is “a byproduct” of the nuclear deal, known as the JCPOA, and was temporary.

Nebenzia was also asked about the controversial matter of the US possibly seeking to use the “snapback” provision in the 2015 Security Council resolution endorsing the nuclear deal, which would restore all UN sanctions against Iran that had been lifted or eased under the terms of the agreement.

The Russian ambassador stressed that “to trigger a snapback you have to be a participant of the JCPOA, and the US proudly announced on May 8, 2018, that they withdrew from the JCPOA and closed the door behind.”

“Now, they knock on the door and say, ‘Now just wait a second we forgot to do one little thing on the JCPOA, but let us back, we’ll do it and we’ll leave again,’” he said.

Nebenzia called the possibility the US invoking snapback “ridiculous,” stressing that “for me it’s unequivocal. They are not members, they have no right” to use any instruments provided by the JCPOA.

He also asked the Trump administration what it would gain from triggering snapback “because snapback will definitely be the end of the JCPOA.”

Nebenzia said the reaction will be that “the most intrusive inspections” of any country which the International Atomic Energy Agency is carrying out in Iran “will cease.”

“My question is, is it in the US interests that it happens?” he asked.

Although Trump pulled out of the deal and described the accord from Barack Obama’s presidency as “the worst deal ever”, the US maintains that it retains the right to invoke a sanctions snapback that the deal envisaged in the event of “significant non-performance” by Iran.

That position rests on a novel State Department legal argument that was first presented in December and asserts that although the US is no longer in the nuclear deal, it remains an original “participant” under the terms of the Security Council resolution that enshrined it.

That resolution does, in fact, list the parties to the 2015 agreement by name, but numerous diplomats in addition to Russia have said the American argument is specious because the Trump administration has made such a point about no longer participating in the deal.

Diplomats say the United States would face a messy battle if it tries to trigger a return of sanctions.

Nebenzia was asked who the legal arbiter of whether the US still has to stand to trigger snapback should be.

“It is up to the members of the Security Council primarily, first of all, and to the remaining participants of the JCPOA itself,” he said.

Nebenzia quoted a letter from Iran’s Foreign Minister Mohammed Javad Zarif to Secretary-General Antonio Guterres on Tuesday in which Zarif says not only the US is “in grave violation” of the 2015 resolution for non-performance, “but it is blatantly attempting illegal paths to reverse the resolution in actual contempt for well-established principles of international law.”

Solely by withdrawing from the JCPOA, the US “has lost any right,” he quoted Zarif as saying.

Nebenzia said he subscribes fully to Zarif’s words, adding, “This to me looks like a truthful legal interpretation.”

The United States has raised with the European parties to deal with the possibility of restoring sanctions if it is unable to get the 15-member Security Council to stop an arms embargo on Iran from expiring.

A resolution to do so needs nine yes votes and no vetoes by Russia, China, the United States, France, or Britain.

Asked if Russia would veto such a resolution, Nebenzia said: “I never answer questions before the right time comes, but you may make a wild guess … I do not see any reason why an arms embargo should be imposed on Iran.”

AP and Reuters contributed to this story.