File photo shows Iranian oil tankers.
Russia has lashed out at the United States over illegal unilateral sanctions imposed against Iran, calling the measures “overt blackmail” and a "crude contradiction of international law."
The Russian Foreign Ministry said in a statement on Monday that the sanctions would harm Moscow-Washington relations.
"Those in Washington should take into account that our bilateral relations will suffer seriously if Russian operators... come under the effects of the American restrictions," the ministry said.
"We are talking about restrictive measures not only against Iran but also affecting foreign companies and individuals working with it, including in the hydrocarbon extraction and transport, petrochemicals, finance and insurance industries," the statement read.
"We consider efforts to... impose internal American legislation on the entire world completely unacceptable," it said.
The statement refers to the measures, approved by the US Congress on August 1, which seek to punish banks, insurance companies, and shippers that help Tehran sell its oil.
The new US sanctions build on Iranian crude sanctions, signed into law by US President Barack Obama, penalizing other countries for buying or selling Iran’s oil. The sanctions took effect on June 28.
Russia also reiterated that unilateral sanctions are counterproductive.
The "constant increase of pressure on Tehran" undermines diplomatic efforts over Iran's nuclear energy program.
The illegal US sanctions are meant to pile up pressure on Iran over its nuclear energy program, which Washington, Tel Aviv, and some of their allies claim may include a military aspect.
Iran refutes the allegation and holds that, as a signatory to the nuclear Non-Proliferation Treaty and a member of the International Atomic Energy Agency, it is entitled to enrich uranium for peaceful purposes.