London, March 24 (RHC)-- Talks over a nuclear deal with Iran are approaching their final week before an end-of-the-month deadline. Both sides have reported progress, but differences remain over the timeline for ending U.N. sanctions and the expansiveness of international inspections.

Speaking ahead of a meeting with European counterparts in London, Secretary of State John Kerry said after substantial progress, in his words, "tough decisions" will be made in the days ahead.

Iran has demanded an immediate end to all United Nations sanctions that have crippled its economy and health sector. In a public address, Iran’s Supreme Leader Ayatollah Ali Khamenei said an end to the sanctions is non-negotiable. Iranian negotiators have also reportedly rejected U.S. demands for inspections of any potential nuclear site, including Iranian military bases.

If a framework deal is reached in the next week, the talks would continue for a final agreement by June.