23 U.S. senators on Saturday sent a letter to President Barack Obama urging him to stand firm during talks with Iran, Reuters reported.
The letter from Democratic senators and one independent was identical to one sent to Obama earlier this week by the House of Representatives, asking that he insist on a final agreement in which Iran would not be able to build or buy a nuclear weapon.
The House letter was signed by 395 of the 435 members of the chamber and was sent as Iran and six world powers met to persuade Iran to scale back its contested nuclear activities.
The 23 senators said they embraced Obama's two-track approach twinning sanctions against Tehran with negotiations, but urged strict procedures of transparency and verification to ensure Iran does not obtain a nuclear weapon.
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.
The sides gathered for another meeting in Vienna this past week, with EU foreign policy chief Catherine Ashton describing them as "substantive and useful", and Iranian Foreign Minister Mohammad Javad Zarif saying he saw "signs" that a long-term nuclear deal could be reached.
As talks have continued, a bill in the Senate to impose more sanctions on Iran has been gaining momentum. Obama, however, has pledged to veto the bill should it pass.
Zarif has warned the United States that if it imposes any new sanctions on his country, the nuclear deal reached in Geneva would be “dead”.