Russia said Saturday that Western sanctions imposed over the conflict in Ukraine had become a stumbling block for the Iran nuclear deal, warning the West that Russian national interests would have to be taken into account.

Iran said Saturday it had agreed a roadmap with the U.N. nuclear watchdog to resolve all outstanding questions about the country's nuclear program by late June, a move seen as a latest push to revive Tehran's 2015 nuclear deal with global powers.

But Russian Foreign Minister Sergei Lavrov said the sanctions on Russia had created a "problem" from Moscow's perspective.

"It would have all been fine, but that avalanche of aggressive sanctions that have erupted from the West – and which I understand has not yet stopped – demand additional understanding by lawyers above all," Lavrov said.

Lavrov said Russia wanted a written guarantee from the United States that Russia's trade, investment and military-technical cooperation with Iran would not be hindered in any way by the sanctions.

"We want an answer – a very clear answer – we need a guarantee that these sanctions will not in any way touch the regime of trade-economic and investment relations which is laid down in the Joint Comprehensive Plan of Action," Lavrov said.

Lavrov said, under the deal, Russia and China would be allowed to help Iran develop its civilian nuclear programs in accordance with non-proliferation rules. Sanctions would not be able to affect those projects, Lavrov said.

"There are still several topics which our Iranian colleagues want more clarity on and we consider those are fair demands," Lavrov said.

"We have asked for a written guarantee ... that the current process triggered by the United States does not in any way damage our right to free and full trade, economic and investment cooperation and military-technical cooperation with the Islamic Republic."

President Vladimir Putin said Saturday that Western sanctions on Russia were akin to a declaration of war and defended Russia's invasion of Ukraine, saying Moscow needed to defend Russian speakers in Ukraine's east as well as its own interests.

Speaking to female flight attendants in comments broadcast on state television, the Kremlin leader said Russia wanted Ukraine to be "demilitarized," "denazified" and Ukraine should have neutral status.