Rep. Adam Smith of Washington, the top Democrat on the House Armed Services Committee, said that, while the deal represents serious progress in the yearslong quest to curb Iran's nuclear ambitions, "far more work remains to be done."
"It is vital that we prevent Iran from obtaining a nuclear weapon in a peaceful way," Smith said.
Obama came into office promising to talk to Iran without preconditions. The U.S. and Iran had severed diplomatic ties in 1979 after the Islamic revolution and the storming of the U.S. Embassy in Tehran, where dozens of Americans were held hostage for more than a year.
The June election of Iranian President Hassan Rouhani, a more moderate-sounding cleric, helped pave the way for a thaw in diplomatic relations with the U.S. and this latest round of nuclear negotiations.
Obama's outreach to Iran has worried Israel and Persian Gulf nations, which fear Iran is using the negotiations as a delay tactic while it continues to pursue a nuclear weapon. The president on Saturday said those nations "have good reason to be skeptical of Iran's intentions." But he said "only diplomacy can bring about a durable solution to the challenge posed by Iran's nuclear program."
Rabbi Steve Gutow, president of the Jewish Council for Public Affairs, said that while "Iran has done little to deserve our trust," the agreement "has the potential to serve as a valuable stepping stone to a final agreement that can serve the long-term security interests of the United States, Israel, the Middle East and the entire international community."
Gutow said any final agreement must not leave Iran able to continue its drive for nuclear weapons capability, or able to easily restart its program at any point in the future.
"The menace of a nuclear-armed Iran needs to be eliminated once and for all," Gutow said.