Russia on Tuesday said it was "deeply disappointed" by US President Donald Trump's decision to re-impose unilateral sanctions on Iran.
"We are deeply disappointed by US steps to reimpose its national sanctions against Iran," the Russian foreign ministry said in a statement.
The ministry said it will do "everything necessary" to save the historic 2015 Iran nuclear deal and protect its shared economic interests with Tehran.
"This is a clear example of Washington violating UN Resolution 2231 (on the Iran deal) and international law," the statement said.
Moscow said the multi-party nuclear agreement Trump abandoned in May has "shown its effectiveness".
It called on the international community "not to allow such significant achievements in multilateral diplomacy to be sacrificed in the name of American aspirations to settle political scores with Iran."
"As long-term experience has shown, it will not be possible to gain concessions from Iran using pressure," the statement said.
The US re-imposed a wave of tough, unilateral sanctions against Iran on Tuesday, bringing back into effect harsh penalties lifted by the deal.
The first of two rounds of US sanctions kicked in at 12:01 am (0431 GMT), targeting Iran's access to US banknotes and key industries, including cars and carpets.
Iranians are already seeing the effects of the sanctions, with Iran's rial currency losing around half its value since Trump announced the US would withdraw from the nuclear accord.
Trump's contempt for the nuclear deal dates back to his time as presidential candidate and on May 8, he made good on a pledge to pull America out of the international agreement.
People walk by murals on the wall of the former US embassy in the Iranian capital Tehran on August 7, 2018 after US President Donald Trump warned countries against doing business with Iran
Moscow said the multi-party 2015 Iran nuclear agreement Trump abandoned in May has "shown its effectiveness"