WASHINGTON — U.S. Sen. Tom Cotton, R-Ark., made clear his deep skepticism of ongoing Iran nuclear negotiations during a Senate Banking Committee hearing Tuesday focused on Iran sanctions.

Cotton peppered Deputy Secretary of State Antony J. Blinken with questions about delays in reaching a final deal for Iran to abandon any ambition for nuclear weapons and opposition to Congress imposing stronger sanctions in light of the delays.

The exchange, which came late in the hearing, left Cotton frightened that the Obama administration continues to negotiate with what it admits is a bad actor and convinced that Congress should act as soon as possible to pass Iran sanctions.

Passage of a sanctions bill does not appear likely ahead of the next soft deadline - March 24 - for the ongoing negotiations to conclude.

New Jersey Sen. Robert Menendez, the co-sponsor of the sanctions bill, said Tuesday that he and other Democrats would not support passing the bill before then.

"Many of my Democratic colleagues and I have sent a letter to the president telling him that we will not support passage of the Kirk-Menendez bill on the Senate floor until after March 24 and only if there is no political framework agreement, because we remain hopeful that diplomacy will work," Menendez said at the hearing.

President Obama issued a veto threat against such sanctions as part of his State of the Union Address last week.

"New sanctions passed by this Congress, at this moment in time, will all but guarantee that diplomacy fails — alienating America from its allies; making it harder to ensure sanctions, and ensuring that Iran starts up its nuclear program again," Obama said.

Cotton and other proponents of the sanctions bill would need significant support from Senate Democrats to overcome a veto.

Still, Cotton "remains steadfast in his belief that Congress needs to pass Iran sanctions as soon as possible," said his communications director Caroline Rabbitt.

The United States, Britain, China, France, Germany and Russia want to secure an agreement to ensure that Iran cannot use its nuclear energy program to develop nuclear weapons in exchange for easing previously imposed sanctions. They have been in negotiations with Iran for 18 months and now hope to have a political understanding by March and a final deal by June 30.

At the hearing, Cotton questioned why the negotiations have not moved as swiftly as Secretary of State John Kerry had initially predicted.

Kerry had estimated it would take three to six months. "Secretary Kerry obviously miscalculated … what was the main miscalculation," Cotton asked.

"I don’t think there was a miscalculation," Blinken said. "Built into the interim agreement was the possibility of extending it and the extension would be based on a determination that we had made enough progress that we could see the possibility of getting to yes."

Cotton then asked if Blinken expected an agreement would be reached by March 24.

"I think the President said it was - How did he put it? - less than 50-50," Blinken said.

Cotton then asked why the United States continued to negotiation despite a series of Iranian provocations in the region - including holding a Washington Post journalist.

"Iran does things every single day in the region, and indeed beyond, that are highly objectionable to us and to most of our partners," Blinken acknowledged.

Why then should we "look the other way" at Iran’s needless provocative acts yet Congress should resist passing new sanctions out of concern for the "delicate sensibilities" of moderate Iranians, Cotton asked.

After a bit of give and take, Blinken said that Iran’s internal politics are "tremendously challenging" making these negotiations a delicate dance.

"Anything we do that reinforces the hand of those who absolutely don’t want a deal under any circumstances is going to weaken their hand and make it less likely that we will get to an agreement," he said.

Rabbitt said that testimony from Blinken reaffirmed Cotton’s belief that strong sanctions are absolutely needed against Iran.

"And, based on his answers today, it’s frightening the Administration actually admits what a bad actor Iran is, yet continues to negotiate," she said.