DUBAI (Reuters) – A senior Iranian cleric said on Friday ending Iran’s economic isolation by lifting banking and oil trade sanctions was Tehran’s most important demand in talks on reviving its 2015 nuclear deal with world powers.

Iran called on the West Wednesday to be “realistic” during the negotiations, after its top negotiator came back to Tehran in preparation for final talks.

Ayatollah Ahmad Khatami stated Friday that “our negotiators… try their best to protect the nation’s interest, but know that the last point is the lifting all sanctions on banking, trade, and other areas,” during prayers held in Tehran.

According to state media, he stated that “if sanctions are not lifted it is like there weren’t any talks.”

Ayatollah Ayatollah Al Khamenei has final authority over the content of Friday prayers sermons. He also determines Iran’s nuclear strategy.

After 10 months of talks in Vienna, progress has been made toward the restoration of the pact to curb Tehran’s nuclear program in exchange for sanctions relief, but both Tehran and Washington have cautioned that still there are some significant differences to overcome.

Last week, Iran’s hardline-led parliament asked for assurances from the United States that it would continue to honor a previously signed agreement. This letter has not been voted upon by the assembly.

A top Iranian official told Reuters Iran’s willingness to compromise by agreeing “inherent guarantee” that the U.S. administration would continue to negotiate an agreement. Washington has stated that President Joe Biden cannot provide Iran the legal assurances it has requested.

Iran is insistent on the removal immediately of all sanctions that have been imposed by former U.S. president Donald Trump.