By Ali Akbar Dareini, Jun. 24, 2015, Yahoo/AP

TEHRAN, Iran (AP) — Iran has hardened its stance less than a week before the deadline for a nuclear deal, with its top leader rejecting a long-term freeze on nuclear research as a constitutional body on Wednesday approved a law banning access to military sites and scientists.

Ayatollah Ali Khamenei also insisted that Iran will only sign a deal if international sanctions are lifted first, which could further complicate the negotiations. The new law calls for all sanctions to be lifted the first day of any agreement's implementation.

The supreme leader has backed his negotiators amid criticism from hard-liners. But his latest remarks may narrow their room to maneuver ahead of a self-imposed June 30 deadline for a potentially groundbreaking deal with world powers that would curb Iran's nuclear activities in exchange for lifting sanctions.

Iran's constitutional watchdog, known as the Guardian Council, ratified the legislation banning access to military sites and scientists, making it binding law, according to state TV.

The bill would still allow for international inspections of Iranian nuclear sites within the framework of the Nuclear Non-proliferation Treaty.