Iranian Supreme Leader Ayatollah Ali Khamenei on Tuesday praised last week's implementation of the nuclear deal and the accompanied lifting of international sanctions against his country, but he  warned that Iran must remain cautious of American intentions, reports AFP.

Khamenei, who has has the final say on all state matters including the nuclear negotiations, made the comments in a letter written to Iranian President Hassan Rouhani to congratulate him on the successful implementation of the nuclear deal signed with the P5+1 world powers. In exchange for Iran agreeing to limit its nuclear program, some U.S. and international sanctions have been lifted, opening Iran's economy to international trade and investment and giving it access to $100 billion in assets that were previously frozen overseas.

"I would like to express my satisfaction because the resistance of the great people of Iran in the face of unjust sanctions, the endeavor of nuclear scientists in advancing this important industry and the untiring efforts of our negotiators, which forced the other sides - some of whom are notorious for their enmity towards the people of Iran - to retreat and to lift part of these bullying sanctions. I would like to thank you, the negotiating team, the honorable Minister and all officials involved," Khamenei said in the letter published on his website.

But he stressed "the need to be vigilant about the deceit and treachery of arrogant countries, especially the United States, in this [nuclear] issue and other issues. Be careful that the other side full meets its commitments."

He added that "statements that some American politicians have made in the last two, three day are cause for deep suspicion."

Khamenei didn't name any specific politicians, but Reuters notes that nearly every Republican presidential candidate has heavily criticized the deal, with several promising to disavow U.S. involvement should they win the election.

Nor did Khamenei mention the new sanctions that the U.S. Treasury imposed on Iran on Sunday after the United Nations determined Iran launched ballistic missiles capable of carrying nuclear warheads, which was a violation of a U.N. ban. Under the sanctions, 11 entities and individuals involved in procuring goods for the ballistic missile program are banned from using the U.S. banking system.

Iran's Foreign Minister spokesman Hossein Jaber Ansari said Monday that the country's "missile program has never been designated to be capable of carrying nuclear weapons" and that the sanctions have "no legal or moral legitimacy," reported BBC. He added: "America sells tens of billions of dollars of weaponry each year to countries in the region. These weapons are used in war crimes against Palestinian, Lebanese and most recently Yemeni citizens."