As the March 31 deadline approaches for a preliminary accord over Iran's nuclear program, Obama administration negotiators are no longer demanding that Iran allow U.N. inspection of suspected weapons sites prior to a deal being struck, and some worry such concessions could prevent the kind of verifiable agreement promised by President Obama.

Following a 2013 interim deal between Iran and world powers, the U.N. International Atomic Energy Association (IAEA) was tasked with making sure Iran is not using civilian energy technology to produce nuclear weapons. U.S. officials previously described such U.N. inspections as crucial to reaching a final deal, as it would reassure the world that Iran's program is peaceful. A final deal would provide sanction relief in exchange for Iran providing verifiable proof that it's not developing nuclear weapons.

President Obama previously insisted that Iran has "abided by the terms of [the interim] agreement. We know what is happening on the ground in Iran. They have not advanced their nuclear program."

But Yukiya Amano, the IAEA director general, recently said that Iran has only replied to one of its dozen inquiries about possible "military dimensions" of the country's nuclear activities, adding that IAEA has been unable to verify whether Tehran has diverted nuclear material away from peaceful operations, reported The Wall Street Journal. Amano said he believes the negotiating nations should insist that Iran allow IAEA inspectors to visit any of its facilities at any time to examine for evidence of secret nuclear weapon development.

President Obama promised his administration would guarantee effective oversight on Iran's nuclear program. "If there is no [verifiable] deal then we walk away," Obama said in a CBS interview.

But as the WSJ noted, negotiators now appear to be caving to Tehran's demands and scaling back their previous oversight requests.

According to the WSJ, "the U.S. and its diplomatic partners are revising their demands on Iran to address these concerns before they agree to finalize a nuclear deal."

"As a result, the U.S. and its negotiating partners are seeking to get Iran's upfront approval to implement a scaled-back version of the IAEA's 2013 agreement with Iran to a 12-step work plan to resolve questions related to possible weaponization work," the WSJ reported. "Under the new plan, Tehran wouldn't be expected to immediately clarify all the outstanding questions raised by the IAEA in a 2011 report on Iran's alleged secretive work. A full reckoning of Iran's past activities would be demanded in later years as part of a nuclear deal that is expected to last at least 15 years."

Reports have also emerged that the U.S. could allow Iran to continue operating nuclear centrifuges at an underground site previously used for uranium enrichment. Negotiators may allow Iran to continue to run hundreds of centrifuges at the site, according to the Associated Press.

Western sources told the Washington Free Beacon that such concessions could allow Iran to continue work related to its nuclear weapons program, as the U.S. is willing to allow Tehran to keep its most controversial military sites closed to inspectors until after sanctions have been lifted. And once Iran begins to block inspectors' access to facilities, as it has done in the past, Tehran's nuclear infrastructure would be protected from a strike by Western forces, the Beacon noted.

"Once again, in the face of Iran's intransigence, the U.S. is leading an effort to cave even more toward Iran-this time by whitewashing Tehran's decades of lying about nuclear weapons work and current lack of cooperation with the [International Atomic Energy Agency]," one Western source briefed on the talks told the Free Beacon on the condition of anonymity.

"Instead of ensuring that Iran answers all the outstanding questions about the past and current military dimensions of their nuclear work in order to obtain sanctions relief, the U.S. is now revising down what they need to do," the source told the Free Beacon. "That is a terrible mistake - if we don't have a baseline to judge their past work, we can't tell if they are cheating in the future, and if they won't answer now, before getting rewarded, why would they come clean in the future?"