WASHINGTON — The Obama administration appeared before both houses of Congress today to explain its four-month extension to the nuclear negotiations with Iran — and tried to draw a distinction between “repealing” sanctions as required by law and “waiving” them via executive authority.

That just stoked concerns of lawmakers in both parties.

“I think everyone knows where I stand. I’ve been skeptical of the Iranians’ sincerity from day one. And I cannot say that I am any less skeptical today than I was six months ago. I do not believe Tehran has had a change of heart about its nuclear program,” Senate Foreign Relations Committee Chairman Robert Menendez (D-N.J.) said at the morning’s hearing.

“I also get concerned when I hear ‘if no deal, what’? Because that implies that you have to get a deal at any cost. And so, I know that there are those in the disarmament community and in the editorial pages who suggest that those of us who really want to make sure that we get a good deal somehow have this penchant for wars.”

Menendez made clear he had no patience for “the State Department’s talking points” but instead wanted to hear “what happened at the negotiating table that brought Iran closer, to their view, to a deal, if only they had another four months.”

“I also want to be clear today that I do not support another extension of negotiations,” he said. “At that point, Iran will have exhausted its opportunity to put real concessions on the table, and I will be prepared to move forward with additional sanctions.”

Ranking member Bob Corker (R-Tenn.) said numbers of classified and unclassified briefings only increased their concerns. “I mean, in each case, on the important issues, we feel the goal post moved,” he said. “…I hope that today you will publicly commit that there will be absolutely no more extensions — none — no matter where we are at the end of this four-month period, there will not be additional extensions.”

Undersecretary of State Wendy Sherman, who has been leading the U.S. team at the P5+1 negotiations, told the senators, “I cannot tell you today that our diplomacy will succeed because I am not sure that it will.”

“I have learned in negotiations that it is very difficult to say what will happen at the end of any given period of time… Our intent is absolutely to end this on Nov. 24 in one direction or another.”

Sherman wouldn’t be clear on how long of an agreement is being sought. Menendez has insisted on a period as long as 30 years, while Iran is suspected of lobbying for short-term concessions to get out of a long-term agreement.

“We believe that the duration of this should be at least double digits, and we believe that it should be for quite a long time,” she said. “I’m not going to put a specific number on the table today, because that is a subject of very sensitive negotiations, but I’m happy to discuss that with you in a classified setting.”

“We did not — we made a very conscious decision not to go for a six-month extension, which was possible under the JPOA because we thought we would just get to month five before anything would happen.”

Corker reminded Sherman of an April 8 statement by Kerry “that the administration is obligated under law to come back to Congress for any relief of statutorily imposed sanctions on Iran, and any agreement with Iran will have to pass muster with Congress.”

“I want you to clearly state to me, will you or will you not come to Congress before lifting — whether it’s a waive, a temporary waive, a skate-down-the-road, whatever, no way will you lift any kind of relief on Iran, period, after this next agreement is reached or not reached without coming to Congress?” he asked.

“We cannot lift any sanctions without congressional action. We can, as you said, suspend or waive under the current legislation. We will not do so without conversations with Congress,” Sherman said. “If you are asking, senator, whether we are going to come to Congress for legislative action to affirm a comprehensive agreement, we believe, as other administrations do, that the executive branch has the authority to take such executive action on this kind of a political understanding that might be reached with Iran. I can’t tell you whether we will or not.”

“So, you’re here telling me you can’t be any more clear than coming and having the same kind of conversation you’ve had in the past when asked this,” Corker said. “You’re telling us what you’re going to do.”

“Senator, the United States Congress and the United States Senate has oversight authority and legislative authority,” Sherman shot back. “You are free to decide what action you think is appropriate, or any executive branch’s decision by any administration.”

But Wendy Sherman and Treasury Undersecretary for Terrorism and Financial Crimes David Cohen faced similar skepticism at the House Foreign Affairs Committee in the afternoon — from the president’s own party.

Rep. Brad Sherman (D-Calif.) noted that Cohen has said sanctions would come down on a nuclear Iran “like a ton of bricks.”

“I think you need more bricks,” he said.