Democrats and Republicans backing a bill to give the U.S. Congress a chance to review a nuclear deal with Iran insisted on Tuesday that it be passed free of controversial add-ons that they claim could scuttle negotiations with Tehran, draw a presidential veto or leave lawmakers with no say on a national security threat.

As written, the legislation would block President Barack Obama from waiving congressional sanctions for at least 30 days while lawmakers weigh in on any final deal the U.S. and five other nations can reach with Iran. And it would stipulate that if senators disapprove the deal, Obama would lose authority to waive certain economic penalties — an event that would certainly prompt a presidential veto.

Democratic Senate Minority Leader Harry Reid warned Republican presidential hopefuls in the Senate not to use it as a "platform for their political ambitions." He said the full Senate should pass the bill with the same bipartisanship that occurred in the Senate Foreign Relations Committee, which unanimously approved the measure 19-0.

The alternative to the bill is not a better bill, he said, "it is a deal without any meaningful congressional input."

The bill has gained the tacit approval from Obama. He says he will sign it as written, but the White House warns that he will reconsider if the measure is substantially changed. Sen. Bob Corker, a lead sponsor of the bill and chairman of the Senate Foreign Relations Committee, said Tuesday that the bill, in its current form, has the support of 67 senators, which is a veto-proof majority.

More than 50 amendments have been introduced so far — all by Republicans.

Democrats have threatened to withdraw their support if un-related amendments distort the bill.

Sen. Marco Rubio, a White House hopeful, wants to amend the bill to require Iran's leaders to publicly accept Israel's right to exist, a nearly impossible mandate. Another presidential candidate, Sen. Ted Cruz, hopes to put the onus on advocates to win congressional approval of a deal, and not on opponents to gather enough votes for rejection.

Senate Republican Majority Leader Mitch McConnell also said preventing Iran from developing nuclear weapons should not be a partisan issue. But he said he would allow vigorous discussion and a robust amendment process as the Senate debates the bill.

"Preventing the world's lead sponsor of terrorism from gaining access to nuclear weapons should be the goal of all senators no matter what party they belong to," McConnell said. "The price of a bad agreement with Iran could be catastrophic."

Among proposed additions to the bill are demands that Iran release any U.S. citizens it is holding and refrain from any cooperation with nuclear-armed North Korea. Another insists that any agreement be treated as an international treaty, requiring two-thirds ratification by the Senate.

That amendment by Sen. Ron Johnson, a Republican, prompted a response from Condoleezza Rice, national security adviser under President George W. Bush.

"The proposed Iranian nuclear agreement is classically an executive agreement and doesn't need to be a treaty with advice and consent of the Senate," she said. "But Congress should be able to opine given that congressionally mandated sanctions would have to be lifted."

Sen. John Thune, a Republican, has filed an amendment that insists on international nuclear inspectors' access to Iranian military sites. Sen. John Barrasso, a Republican, wants to restore a section of the initial bill that would require the president to certify every 90 days that it is not engaged in supporting terrorism against America.

"It is true that the negotiations under way have nothing to do with alleviating any kind of terrorist sanctions, human rights sanctions or ballistic missile testing sanctions," Corker said. "Should Iran commit an act of terrorism against an American, sanctions would be the minimum thing, I think, they'd have to be worried about. I think bombs and missiles on heads would be the thing they'd have to be concerned about."