The U.S. State Department said Monday that working to curb Iran's nuclear ambitions is in Russia's own interest and not a favor to Washington. Moscow has threatened to cut back cooperation on Iran because of new U.S. non-proliferation sanctions on a Russian company. VOA's David Gollust reports from the State Department.

The State Department says Russia would only be harming its own interests if it follows through with a threat to curtail cooperation with other major powers on preventing Iran from acquiring nuclear weapons.

The Russian warning came from Foreign Minister Sergei Lavrov, who angrily protested a U.S. decision announced Friday to impose non-proliferation sanctions against 13 foreign companies including Russia's state arms exporter, Rosoboronexport.

A State Department announcement, published in the U.S. government's official journal, the Federal Register, did not specify charges against the Russian firm.

But it did say there was credible information that it violated U.S. laws curbing sales of weapons of mass destruction and missile technology to Iran, North Korea and Syria.

Rosoboronexport had previously been sanctioned in 2006 in a move protested by Moscow, and the decision Friday extends U.S. penalties against it for another two years.

Russian Foreign Minister Lavrov, at a news conference in Luxembourg Friday, called the U.S. sanctions against the Russian firm illegal and unjust, and said they undermine cooperation among the five permanent U.N. Security Council member countries and Germany, the P5+1 group, to get Iran to stop enriching uranium.

At a news briefing, State Department Spokesman Sean McCormack confirmed that Moscow had made a similar complaint about the sanctions move through diplomatic channels. He said Russia would only be harming itself if it cut back its role in the P5+1.

"This is not a favor to us. Iran having a nuclear weapon is not in Russia's interest. It is in nobody's interest. So, working diplomatically to see that they do not have the abilities and the know-how and the technologies and the hardware to solve some of the toughest problems that could lead to a nuclear weapon is in Russia's interest," he said.

State Department officials said the reasons for penalizing the Russian firm and the others were classified, but Lavrov indicated it had to do with Rosoboronexport dealings with Iran.

Lavrov said all Russian military-technical cooperation with Iran is in strict accordance with international law, and called the U.S. move an arrogant extra-territorial exercise of American law.

The action bars all U.S. government business dealings with the Russian company and its subsidiaries, and sales to them of U.S. military hardware and technology.

Other foreign entities named in the sanctions announcement are Iran's Revolutionary Guards Corps, three companies from China, two each from North Korea and Sudan, and one each from Syria, Venezuela, South Korea and the United Arab Emirates.