Secretary of State John Kerry doesn't want Congress to approve any new sanctions on Iran while negotiations continue with Tehran about its nuclear program, which the U.S. and its allies worry could eventually produce nuclear weapons.
Kerry plans to brief members of the Senate Banking Committee on Wednesday.
State Department spokeswoman Jen Psaki said Tuesday that he will make clear that putting any new sanctions in place "would be a mistake."
She says that Kerry, as a senator, voted in favor of Iranian sanctions several times, but that a vote for or against sanctions right now is really a "vote for or against diplomacy."
Discussions between Iran and world powers failed to reach an agreement last week in Geneva, but another round of diplomacy is planned for next week.