Barack Obama
Barack ObamaFlash 90

Two U.S. senators, who led a push for more sanctions on Iran during negotiations over its nuclear program, on Monday called on President Barack Obama to impose more restrictions if Tehran pursues an energy barter agreement with Russia, Reuters reported.

Last week it was reported that Tehran and Moscow had made progress toward an oil-for-goods deal that sources said could be worth $20 billion and enable Iran to boost vital energy exports in defiance of Western sanctions.

In the wake of that report, senators Robert Menendez and Mark Kirk wrote to Obama and said that if Iran moved forward with the plan, Washington should respond by reinstating sanctions eased under a preliminary nuclear agreement, rigorously enforce reductions in global purchases of Iranian crude and punish any violations to the fullest extent of the law.

"We urge you to put Iran on notice that United States is prepared to re-instate these sanctions should Iran attempt to evade our sanctions and violate the terms of the JPA (preliminary agreement)," wrote Menendez, a New Jersey Democrat, and Kirk, an Illinois Republican, according to Reuters.

The two senators were the lead sponsors of a bill introduced late last year to impose new sanctions on Iran if international negotiations on curbing its nuclear ambitions falter.

The bill was gaining momentum in Congress, but Obama lobbied hard against it and has more than once threatened to veto the bill if it passes.

The measure has never been brought the floor for a vote, but Menendez, chairman of the Senate Foreign Relations Committee, has said he is prepared to push for it again when the time is right.

Under a six-month interim deal which was reached in November and went into effect in January, Iran agreed to freeze its uranium enrichment program in return for sanctions relief worth some $6-7 billion, including the transfer of some $4.2 billion in frozen overseas funds.

That interim agreement is meant to lead to a final accord that minimizes any potential Iranian nuclear weapons threat in return for a full lifting of sanctions.

A new round of senior-level negotiations between Iran and the United States, Britain, France, Germany, China and Russia will be held Vienna on Tuesday and Wednesday.