Iran has removed the core of its heavy-water nuclear reactor in Arak and filled it with cement, the BBC reported on Monday, citing Iran’s semiofficial Fars news agency.

The fate of the reactor was one of the sticking points in nuclear negotiations between Iran and the six world powers, which reached a deal in July of last year.

Under the terms of the deal, Iran agreed the heavy-water reactor would be reconfigured so it was not capable of yielding material for a nuclear weapon.

Behrouz Kamalvandi, the spokesperson for Iran’s atomic energy agency, told the Etemad newspaper on Monday Iran “has met its commitments under the July nuclear agreement earlier than expected”.

“Implementation of JCPOA will finish in the next seven days,” he said.

Satellite images from several years ago showed that the Arak plant was operational, raising fears that it is trying to produce plutonium for a nuclear bomb. Iran invited inspectors to visit the plant a year later, shortly after an interim agreement was signed with world powers.

Removing the core of the heavy water reactor to produce less plutonium is a crucial step before the relief from sanctions starts as part of the July agreement.

In November, it was reported that the six world powers would help Iran redesign the reactor so that it cannot produce weapons-grade plutonium.

There have been indications in recent weeks that implementation of the July agreement is around the corner, despite a December 2 report from the International Atomic Energy Agency (IAEA) which concluded that Iran made a “coordinated” effort to develop nuclear weapons in the past, although the efforts apparently ended at an early stage.

According to the BBC, Iranian President Hassan Rouhani said in a speech broadcast live on state television on Monday, “We are hopeful that the sanctions against Iran will be lifted in the next few days.”