The Iranian government will begin fully implementing the landmark nuclear deal reached with world powers “with good will,” and the work will be done while keeping in mind concerns voiced by Iran’s supreme leader, President Hassan Rouhani said Thursday.

A letter posted on Rouhani’s website, president.ir, addressed to supreme leader Ayatollah Ali Khamenei said Iran will be keeping close watch to make sure other parties to the deal fulfill their obligations.

“The government of the Islamic Republic of Iran will start ‘full implementation’ of the Joint Comprehensive Plan of Action with good will and based on Your Excellency’s considerations and requirements and the decisions of the Supreme National Security Council and the Parliament,” Rouhani said in the letter.

“The other side’s fulfillment of its obligations will be vigilantly monitored and the Supreme National Security Council will adopt the needed decision to take the proper course of action,” he said.

Khamenei on Wednesday endorsed the deal but warned the government to be vigilant, saying the United States cannot be trusted.

He also said the agreement “suffers from multiple structural weaknesses and ambiguous points that can lead to present and future great harms to the country in the absence of precise and constant vigilance.” He added that “any remarks saying the structure of sanctions will remain in place are considered a breach” of the agreement.

The agreement reached in July with the U.S., Britain, France, China, Russia and Germany curbs Iran’s nuclear activities in exchange for lifting crippling international sanctions.

Western nations have long suspected Iran of pursuing nuclear weapons alongside its civilian program, charges rejected by Tehran, which insists its program is entirely peaceful.

The agreement has been the subject of fierce debate within Iran, with hard-liners arguing that the negotiators gave up too much ground. They also fear the agreement could lead to a broader rapprochement with the United States, which they deride as the “Great Satan.”

Khamenei’s expression of support hands Rouhani’s moderate camp a major victory ahead of parliamentary elections.

(AP)