A ban on conventional weapons sales to Iran ends on October 18 and the United States has threatened to try to force a return of UN sanctions if it is not extended.

Pompeo said the United States would submit the long-awaited resolution next week and said he was alarmed at indications that China was already preparing arms sales to Iran.

"There are nations lining up to sell weapons that will destabilize the Middle East, put Israel at risk, put Europe a risk, risk American lives as well," Pompeo told reporters.

"We're not going to let it happen. And so we're using every diplomatic tool we have in the tool-kit," he said.

Russia and China wield veto power on the Security Council and want the embargo to expire as laid out under a 2015 resolution.

That resolution had blessed a denuclearization deal with Iran negotiated by then US president Barack Obama from which President Donald Trump pulled out, denouncing it as a blunder.

But Pompeo has offered the contested argument that the United States remains a "participant" in the 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.

Pompeo pointed to Iranian support to Yemen's Huthi rebels, who are under assault from US ally Saudi Arabia, as an example of an arms violation.

Even European allies of the United States have been skeptical on whether Washington can force sanctions and warn that the attempt may delegitimize the Security Council.

The Europeans support extending the embargo but say the priority should be to preserve the nuclear accord -- which is backed by Joe Biden, Trump's presumptive Democratic rival in November elections.

Pompeo ran into wide skepticism when he directly pressed the Security Council on the arms embargo in June.

Iran says it has the right to self-defense and that a continuation of the ban would mean an end to the nuclear deal.

Iran's foreign minister, Mohammad Javad Zarif, said last month that his government was negotiating a 25-year accord with China, the main country that has been willing to defy unilateral US sanctions on Tehran.