Both Democratic and Republican senators are dismissing President Obama's threat to veto a bill containing new Iran sanctions, setting up a showdown between Congress and the executive that will transcend party.

At issue: the slow pace of negotiations with Iran over curbing their nuclear program and the lack of confidence that members on both sides of the aisle hold in the ability of the Obama administration to get a good deal.

Politico:

Democratic and Republican senators on Sunday rebuffed President Barack Obama’s recent warning to Congress not to renew sanctions against Iran.

On Friday, the president said chances of a military conflict with Iran would increase if Congress renewed sanctions on Iran. And he asked Congress “to hold off for a few months” to allow diplomats to negotiate a deal with Iran over its development of nuclear weapons, vowing to veto any new Iran sanctions bill.

On Sunday, Sen. Ron Johnson (R-Wis.), chairman of the Senate Homeland Security Committee, said he has no faith that the Obama administration will finalize a good deal with Iran, and that a weak deal would be worse than no deal at all.

“Imposing additional sanctions is the only way to bring Iran to the negotiating table,” Johnson said on “Fox News Sunday.”

Appearing with Johnson on the program, Sen. Ben Cardin (D-Md.) said if the negotiations languish, then Congress should pass tougher Iranian sanctions.

Negotiations are already languishing, as two deadlines to conclude the talks have passed with no sign that the Iranians are serious about making a deal acceptable to the West.  In fact, the longer the negotiations go on, the more concessions are being offered by the Obama administration, which is desperate to make a deal to cement the president's legacy.

Hardly a compelling reason to strike a deal.

In truth, without our allies signing on to the new sanctions, they would be meaningless.  We don't do much business with Iran as it is, and the pressure we can bring to bear is more psychological in nature than grounded in the reality of international trade.  The kinds of sanctions being discussed include financial restrictions on individuals in the Iranian government, including members of the Revolutionary Guards.  They may put a crimp in their shopping expeditions to Paris, but beyond that, there isn't much pain.

But as a symbol of American commitment, they are important.  And there may be enough Democrats worried about Iranian nukes to join Republicans in overriding any Obama veto of new sanctions.

“If they move in that direction, we will pass tougher sanctions,” Cardin said. “The question is when we will do it, and that’s the issue in discussions on Capitol Hill.”