WASHINGTON (Reuters) - The United States has moved to disrupt an Iranian-Russian network that it said had sent millions of barrels of oil to Syria and hundreds of millions of dollars to indirectly fund militant groups Hamas and Hezbollah.

FILE PHOTO: A youth works at a makeshift oil refinery site in Marchmarin town, southern countryside of Idlib, Syria December 16, 2015. REUTERS/Khalil Ashawi

The complicated arrangement, described by the U.S. Treasury in a statement on Tuesday, involved a Syrian citizen allegedly using his Russia-based company to ship Iranian oil to Syria with the aid of a Russian state-owned company.

Syria then helped transfer hundreds of millions of dollars in cash to Hezbollah, which functions as a political party that is part of the Lebanese government and as a militia, as well as to Hamas, the Palestinian group that rules the Gaza Strip.

The U.S. Treasury Department alleged that since 2014, vessels carrying Iranian oil have switched off transponders to conceal deliveries to Syria.

The Treasury, the State Department and the U.S. Coast Guard have issued an advisory to the maritime community about the sanctions risks of shipping oil to Syria’s government.

Russia will continue supplying oil to Syria in line with its agreement with Damascus despite pressure from the United States, RIA news agency quoted Oleg Morozov, a member of the Russian Federation Council, as saying late on Tuesday.

“The political defeat in Syria apparently prompts the United States to return to the idea of regime change in Damascus. Therefore, economic pressure through oil supply shutdown becomes a tool of the new economic war with (Syrian President) Bashar al-Assad and indirectly with Moscow and Iran,” he said.

Morozov said Russia acts and will act “absolutely legally”.

“We have an agreement with Syria and therefore it’s up to us to decide what we supply and to whom. This will be our answer, (it is) much more effective than counter-sanctions,” he added.

The Russian Energy Ministry declined immediate comment.

An Iranian Foreign Ministry spokesman called the sanctions “fruitless, illogical and inefficient”.

Bahram Qasemi was quoted as saying by state news agency IRNA on Wednesday: “Those who designed and implemented these sanctions will understand sooner or later that they will not achieve their goals.”

The alleged arrangement shows how Russia has sought to undercut U.S. policy toward Syria, where Washington and Moscow back opposite sides of a civil war that began in 2011, as well as toward Iran, which the United States wants to curb its nuclear and missile programs and support for militant proxies.

“Today we are acting against a complex scheme Iran and Russia have used to bolster the Assad regime and generate funds for Iranian malign activity,” U.S. Treasury Secretary Steven Mnuchin said in a statement announcing sanctions on those it said were tied to the network.

“Central Bank of Iran officials continue to exploit the international financial system,” he added.

TARGETS

Richard Nephew, a sanctions expert at Columbia University, said: “The arrangement exposes Russia’s efforts to support Assad for their own interests, which has the function of thwarting the U.S. desire to no longer have Assad in power.”

Those targeted include Syrian Mohammad Amer Alchwiki and his Russia-based company Global Vision Group, which were central to the delivery of Iranian oil to Syria and the transfer of funds to the Islamic Revolutionary Guard Corps’ Quds Force’s “lethal proxies”, the Treasury Department said in a statement.

Other targets include Syrian national Hajji Abd Al-Nasir, Lebanese national Muhammad Qasim Al-Bazzal and Russian national Andrey Dogaev, as well as Iranian nationals Rasoul Sajjad and Hossein Yaghoubi Miab, the statement said.

Sajjad and Yaghoubi, Central Bank of Iran officials, worked to facilitate Alchwiki’s transfers, it said.

Others sanctioned include state-owned Russian company Promsyrioimport, a subsidiary of the Russian Energy Ministry, which the U.S. Treasury alleges had facilitated shipments of Iranian oil to Syria, as well as Mir Business Bank and Iran-based Tadbir Kish Medical and Pharmaceutical Company.

The Treasury’s “designation” of the individuals and entities effectively cuts them off from the global financial system by blocking any of their assets under U.S. jurisdiction and in effect warning non-U.S. institutions against dealing with them.

The United States is at odds with Britain, France and Germany as well as with Russia and China over U.S. President Donald Trump’s May 8 decision to abandon the 2015 Iran nuclear deal, negotiated with the other world powers during Democratic President Barack Obama’s administration.

That agreement removed many U.S. and other economic sanctions from Iran in return for Tehran’s commitment to curtail its nuclear program.

Trump restored U.S. sanctions on Nov. 5 and has threatened more action to stop its “outlaw” policies.

Iran, in turn, called Trump’s actions economic warfare and vowed to defy the sanctions. European powers that continue to back the nuclear deal said they opposed the reapplication of sanctions.