"We are concerned that the interim agreement would require us to make significant concessions before we see Iran demonstrably commit to moving away from developing a nuclear weapons capability," the senators wrote in the letter.
The senators said media reports indicated that the administration would accept a deal that would provide Iran relief from sanctions without forcing the nation to completely stop its work toward developing a nuclear weapon.
"While the interim agreement may suggest that Iran could be willing temporarily to slow its pursuit of a nuclear weapons capability, it could also allow Iran to continue making some progress toward that end under the cover of negotiations," the senators added.
White House spokesman Jay Carney on Tuesday said that the first phase of the agreement with Iran would stop its nuclear weapons program.
"The first phase does envision rolling back as well as halting progress," Carney said during a press briefing.
He also said that the drafted deal "does not roll back sanctions." Carney added that any relief from sanctions would be "temporary and limited and reversible."