Mohammad Javad Zarif
Mohammad Javad ZarifReuters

Iranian Foreign Minister Mohammad Javad Zarif on Sunday blasted the United States and called it "unreliable".

"What the United States is doing, in addition to being unpredictable -- which might sometimes work -- is proving that it is unreliable," Zarif told CNN, as quoted by AFP.

His comments come as the Trump administration contemplates whether to declare that Iran is complying with the nuclear deal it signed with world powers in 2015.

The deal lifts economic sanctions put in place in 2005 in exchange for curbs to Tehran's nuclear program.

President Donald Trump has long been a vocal critic of the Iranian nuclear deal, and he repeated his criticism of the deal in his speech at the UN General Assembly this past week.

Trump called the deal "an embarrassment" to the U.S. and "one of worst and most one-sided transactions the United States has ever entered into."

Trump is due to update Congress by October 15 on whether Iran is in compliance with the nuclear deal.

Should Trump say that Iran is not in compliance with the deal, Congress would have 60 days to decide whether to reimpose sanctions waived under the deal.

While he recently confirmed that Iran is adhering to the nuclear agreement, he and other officials in the administration stressed that the President still has reservations about the deal.

Trump cast further doubt over the deal after the Islamic Republic tested a new medium-range Khoramshahr missile Saturday.

"Iran just test-fired a Ballistic Missile capable of reaching Israel. They are also working with North Korea. Not much of an agreement we have!" Trump tweeted.

Zarif brushed off the threats on Sunday, saying Washington cannot act alone to end the agreement.

"This is not a bilateral agreement. It's not even a multilateral treaty. It's a Security Council agreement and the United States is a member of the Security Council," he argued.

The foreign minister added that Trump's certification of whether Iran is abiding by the deal is an "internal procedure" that in itself does not endanger the agreement.

"The only authority that has been recognized in the nuclear deal to verify is the IAEA," he stressed.

Zarif added that Iran will "consider its options" if Trump tells Congress on October 15 he believes it is not complying with the deal and it is not in U.S. interests to stick by it.

"Iran has a number of options, which include walking away from the deal and going back with greater speed with its nuclear program, which will remain peaceful -- but which will not address and accept the limitations that we voluntarily accepted over our nuclear program," Zarif said.

The Iranian foreign minister sharply criticized Trump following his speech last week, calling them “shameless and ignorant”.

Zarif also said Trump’s remarks showed his lack of knowledge about Tehran’s fight against terrorism.