WASHINGTON (AP) — Secretary of State John Kerry played defense Wednesday on Capitol Hill, fielding dozens of questions from lawmakers worried about what Iran could get in a deal being negotiated to block its ability to make an atomic weapon.

California Republican Rep. Ed Royce, chairman of the House Foreign Affairs Committee, told Kerry at a hearing that members of the panel have serious concerns about the direction of the more than 1-year-old talks, which are at a critical juncture. Negotiators are rushing to try to meet a March 31 deadline for a framework agreement between Iran and the US and five other world powers.

“I’m hearing less about dismantlement and more about the performance of Iran’s nuclear program,” Royce told Kerry. “That’s particularly disturbing when you consider that international inspectors report that Iran has still not revealed its past bomb work.”

New York Rep. Elliot Engel, the ranking Democrat on the committee, expressed skepticism too.

Engel noted news stories claiming that negotiators are willing to ease limits on Iran’s enrichment production during the later years of an accord in order to bridge the differences between the two sides over how long an agreement should last.

“We’re hearing troubling reports on the scale and duration of the program that Iran may be allowed as part of a deal,” Engel said.

The secretary testified in the House two days after returning to Washington from the latest round of talks in Geneva. US and Iranian officials reported progress on getting to a deal that would clamp down on Tehran’s nuclear activities for at least 10 years but would then slowly ease restrictions.

Any comprehensive pact could ease 35 years of US-Iranian enmity — and seems within reach for the first time in more than a decade of negotiations.

Royce said the UN’s International Atomic Energy Agency is worried about the scope of Iranian military-related activities, including its work in designing a nuclear payload for a missile.

“The IAEA inspectors have amassed over 1,000 pages which showed research, development and testing activity on technologies needed to develop a nuclear weapon,” the congressman said. “Of the 12 sets of questions that the IAEA has been seeking since 2011, Iran has answered part of one of them,” adding the Iranians are withhold information on the remaining set.

“They are legitimate and the questions have to be answered,” Kerry replied. “And they will be if they (the Iranians) want to have an agreement.”

He said Iran has complied with all the provisions of a first-step agreement, which launched the talks. “They agreed to roll back their program,” Kerry said. “I think that’s cause for hope.”

Wednesday was Kerry’s second appearance before Congress in as many days. As he did on Tuesday in the Senate, Kerry declined to disclose details of the discussions and told members of the House that it’s inappropriate to condemn what is in an agreement before anybody knows what it is — or even if there even will be a deal.

“It’s fair to be skeptical until you see the agreement, and it’s important to be hopeful. And that’s the way I’d put it,” Kerry said. “I’m not sitting here expressing confidence. I’m expressing hope, because I think we are better off with a viable, acceptable, good, diplomatic agreement than with the other choices. But it remains to see whether or not we can get that kind of agreement.”

“There are some big issues yet to be resolved. We are not there yet,” he said.