Iran is aiming to strike an accord with six powers by June 30 that would curtail its nuclear program in exchange for relief from sanctions. But negotiators have hit an impasse in part over how much enhanced access International Atomic Energy Agency inspectors should have to Iranian sites.

“Iran will absolutely not allow its national secrets to fall into the hands of foreigners through the Additional Protocol or any other means,” Rouhani said in a televised news conference, referring to an IAEA provision that would allow more intrusive inspections in the Islamic Republic.

U.S. and French diplomats have called for Iran to accept stringent measures including granting inspectors access to its military sites as well as inspections on as little as two hours notice — access that the Protocol could encompass.

Rowhani said Iran could embrace the Protocol, noting that other states that are signatories to the nuclear Non-Proliferation Treaty (NPT) had done so without problem. But he insisted Iran should not face especially far-reaching measures.

“A problem we face on many issues is that when we reach a framework in one meeting, our negotiating partners go back on it in the next meeting,” said Rowhani, a pragmatist elected in 2013 on a platform of limited Iranian engagement with the West, after many years of deepening hostility.

“If the other side sticks to the framework that has been established, and does not bring new issues into play, I believe it can be solved… But if they want to take the path of brinkmanship, the negotiations could take longer.”

The IAEA has long had regular, if limited, access to Iran’s nuclear-related sites. But Tehran has refused to let the agency visit military sites, citing the risk of security-sensitive information being passed on to Western intelligence agencies.

The U.S. ambassador to the IAEA, the U.N. nuclear watchdog, said on Thursday that additional nuclear transparency measures were outlined in a preliminary deal reached in April between Iran and its negotiating partners.

Supreme Leader Ayatollah Ali Khamenei, who has the final word on Iran’s foreign and security policy, has ruled out several requests by the West, including on interviewing its nuclear scientists and “extraordinary supervision measures.”

The Additional Protocol would also permit the IAEA to collect environmental samples like soil that can unearth military dimensions to nuclear activities years after they have taken place.

Western powers have long suspected Iran of trying to develop the means to make atomic bombs, while Iran insists its uranium enrichment programme is purely for peaceful purposes.

Rowhani said: “What is important to Iran is that, in implementing this protocol, we make it clear to the world that the accusations we have faced about trying to build a bomb are baseless.”