Sen. Bob Corker (R.-Tenn.), chairman of the Senate Foreign Relations Committee, wants nuclear negotiations with Iran to stretch past a deadline. (Reuters)

The chairman of the Senate Foreign Relations Committee said Wednesday that he had urged Secretary of State John F. Kerry to ignore a looming deadline for ­nuclear negotiations with Iran if that’s what it takes to secure a more ironclad deal.

Sen. Bob Corker (R-Tenn.), a key figure in brokering a compromise bill acceptable to the White House and congressional skeptics of an Iran deal, said he spoke with Kerry by phone late Wednesday afternoon, a day after Kerry said the United States is not “fixated” on Iran accounting for every last bit of its past secret nuclear research. Corker has said he thinks the administration is softening its positions in a rush to strike a deal by a self-imposed June 30 deadline.

“June 30 is an artificial deadline,” Corker said he told Kerry. “If it takes longer to get the right deal, take longer, please. Don’t start cutting corners. I know group dynamics; when you’re close to the end of a deal, and your aides are pushing part of what’s going to be a major legacy, I understand how that can affect things. But please, please stop!”

Going much past the deadline could cause problems for the administration, however. Congress has 30 days to review any deal and vote, if the lawmakers choose, on a resolution of disapproval. If they get it after July 10, the review period grows to 60 days.

But Corker’s remarks underscore growing concerns in Congress about negotiations with Iran to rein in its nuclear program in exchange for lifting sanctions. The United States is one of six world powers negotiating with Iran, and Kerry has played a dominant role in the talks, which have produced a temporary framework agreement. Kerry is expected to join discussions in Europe soon in a push for a final deal.

In his first State Department news conference since he broke his leg in a bicycle accident on May 31, Kerry on Tuesday said the United States is more concerned about preventing Iran from acquiring nuclear weapons in the future than with extracting a confession from Iran about past secret work that Iran has long denied conducting. One of the sticking points in the talks has been how much access Iran will grant investigators from the International Atomic Energy Agency trying to account for the “possible military dimensions” of the work, meaning whether Iran was trying to build nuclear weapons.

Kerry’s remarks, made in a video news conference from his home in Boston, seemed to suggest that the United States could agree to easing sanctions before the IAEA resolves all its outstanding questions. But on Wednesday, Kerry spokesman John Kirby said the secretary’s remarks were misinterpreted and the United States would not agree to lift any sanctions before the IAEA gets all the access it seeks.

“Sanctions-lifting is only going to occur as Iran meets agreed-to steps, including addressing the concerns IAEA has over possible military dimensions,” Kirby said.

Corker said that he had heard remarks similar to Kerry’s during a series of briefings by administration officials in the past month. Corker has written letters he characterized as “strident” to the administration, hoping to stiffen its spine to resist any backsliding, he said.

“They have a fixation on ‘We don’t want to offend Iran’s national pride by forcing them to come clean,’ ” he said.

“Are you kidding me?” he added with a touch of sarcasm.

But Corker said he considers getting Iran to account for its secret weapons work a key issue so nuclear experts can better assess the country’s potential ability to build nuclear weapons.

“The experts all emphasize it’s important to get it on the front end,” he said.