(CNN)Senate Republicans are hammering President Barack Obama's administration over an Iran nuclear deal that hasn't even been announced yet.
Senate Republicans remain skeptical of pending Iran deal
And as they laid into the negotiations, they said Obama might struggle to get 34 out of 100 senators -- the number he'll need to implement the deal -- to back him.
"We already know that it's going to leave Iran as a threshold nuclear state. We know that," Senate Majority Leader Mitch McConnell, R-Kentucky, said on "Fox News Sunday."
"It appears as if the administration's approach to this was to reach whatever agreement the Iranians are willing to enter into," he said. "So I think it's going to be a very hard sell -- if it's completed -- in Congress."
Negotiators in Vienna have said they're close to striking a deal that would thwart Iran's nuclear ambitions, limit the country's centrifuges and increase inspections in exchange for the lifting of economic sanctions that have strained the Iranian economy.
But the deal has long been opposed by Republicans who say Obama has given Iran too much -- especially since many of the deal's provisions would expire in 10 to 15 years.
They offered a new round of criticism Sunday, amid reports that a deal could be imminent.
Senate Foreign Relations Committee Chairman Bob Corker, R-Tennessee, said on NBC's "Meet the Press" that Tehran will "cheat by inches" and he doesn't believe it'll be possible to verify that the country has abandoned its nuclear ambitions.
Sen. Tom Cotton, R-Arkansas, said on CBS's "Face the Nation" that the United States needs to push Iran with a "credible threat of military force" and by walking away from the negotiating table, rather than extending the window for diplomacy.
"Whatever deal comes out of this weekend is going to be dangerous for the United States and dangerous for the world," Cotton said.
Sen. Lindsey Graham, the South Carolina Republican who is seeking the party's 2016 presidential nomination, said on CNN's "State of the Union" that an ideal arrangement for now is to leave an interim agreement with Iran in place and let Obama's replacement as president finalize the deal.
He said every Republican candidate, except for Kentucky Sen. Rand Paul, would do better than Obama has.
That, Graham said, is because Obama's administration is "weak in the eyes of the Iranians."
"Getting a bad deal with Iran is the worst possible outcome because it's going to start a nuclear arms race, and under the agreement they're talking about, you're ensuring they're going to become a nuclear power," Graham told CNN's Dana Bash.
"The goal was to dismantle their program," he said. "Now we're going to lock it in place."