Simorgh rocket is launched and tested at the Imam Khomeini Space Centre, Iran, in this handout photo released by Tasnim News Agency on July 27, 2017. (Xinhua/REUTERS)

MOSCOW, Aug. 16 (Xinhua) -- Moscow hopes the United States will refrain from unilateral steps leading to the collapse of the 2015 nuclear agreement with Iran, Russian Foreign Minister Sergei Lavrov said here Wednesday.

"I hope that the United States will not violate the obligations it has assumed," Lavrov said at a press conference.

Iranian President Hassan Rouhani warned Tuesday that Iran's nuclear program could be restarted within hours if the U.S. administration imposes additional sanctions on Tehran.

The U.S. Congress earlier this month approved a series of new sanctions against Iran for its ballistic missile program and other activities in the region.

Iran said these tests did not go against the Joint Comprehensive Plan of Action it signed in July 2015 with the United States, Russia, China, France, Britain, Germany and the European Union on stopping its nuclear program.

Lavrov condemned the new U.S. sanctions as illegitimate and capable of "undermining and destroying the carefully built balance" reached to curb Iran's nuclear program.

He said Russia upholds the principle of abstaining from unilateral sanctions but honors the measures of influence agreed upon within the United Nations (UN) Security Council.

"The Americans are categorically against the principle ... We will necessarily defend it (the principle) in all future discussions," Lavrov said.