FNA- Iranian Supreme Leader's top aide Ali Akbar Velayati, who is also a ranking member of Iran's nuclear deal monitoring commission, warned that the US president's endorsement of the Iran Sanctions Act (ISA), recently approved by the Senate, will meet Tehran's firm response.

"Members of the monitoring commission unanimously agree that if the extension of sanctions act is signed by the US president, it will violate the nuclear deal and certainly the Islamic Republic of Iran will give an appropriate, clear and firm response to it," Velayati said in a press conference in Tehran on Tuesday.

He said that the commission will decide about Iran's response to Washington's violation of the nuclear deal.

His remarks came after the US Senate voted to the extension of the Iran Sanctions Act (ISA) on Thursday that clearly violates the last year nuclear deal. The approval now waits for US President Barack Obama's endorsement. Iranian officials have warned that Tehran has prepared itself for showing a tough reaction.

On Monday, Iranian Foreign Minister Mohammad Javad Zarif and his Chinese counterpart Wang Yi underlined the necessity for all parties to the last year nuclear deal to remain committed to their undertakings.

"The Joint Comprehensive Plan of Action is a multilateral document approved by the UN Security Council and internal developments of countries shouldn’t distort it," Wang said during the meeting in Beijing.

At the meeting, the two high-ranking officials also underlined the necessity for other members of the Group 5+1 (the US, Russia, China, Britain and France plus Germany) to remain fully committed to the Vienna nuclear deal signed with Tehran last year.

They also emphasized serious fight against terrorism and mutual cooperation in this regard.

On Sunday, Iranian President Hassan Rouhani warned the US of Tehran's firm response to the implementation of the Iran Sanctions Act whose extension for another 10 years was approved by the Senate earlier this month and waits for President Barack Obama's endorsement.

"As stressed by Supreme Leader (Ayatollah Khamenei), the Islamic Republic of Iran has and will never violate the nuclear deal; we are committed to our undertakings and I, as the president and head of the Supreme National Security Council (SNSC), declare clearly that we will not bear violation of the Joint Comprehensive Plan of Action (JCPOA) by any members of the G5+1 and will respond it properly," President Rouhani said in Tehran, addressing the Iranian MPs in a session to submit the next year budget plan to the parliament for approval.

Stressing that the US congress's extension of the ISA is against the JCPOA, he said, "The US president is required to use his authorities and prevent its approval and specially implementation. I declare clearly that if the approval is implemented, it will clearly violate the nuclear deal and will be followed by our firm response; we even consider its endorsement by the US president against the US undertakings and it will face appropriate reaction."

President Rouhani had also on Saturday requested the world powers, party to the nuclear deal with Tehran, to take action to stop Washington from damaging the Vienna agreement, warning that the US is treating the multilateral deal based on its own antagonistic aspirations.

"The nuclear deal is the product of seven countries' cooperation and in line with global peace and security. Every one should try to safeguard its achievements and we shouldn’t allow any country to take action to weaken the agreement as it desires," President Rouhani said in a meeting with Russia's special envoy on Syria, Alexander Lavrentiev, in Tehran.

"Iran has always been and will be committed to its international undertakings and other members of the Group 5+1 should fully act upon their undertakings too for the nuclear deal to remain," he added.

Lavrentiev, for his part, referred to the developments related to the nuclear deal, and said, "Russia's position on the nuclear deal is stable and strong and undermining the agreement is no way justified."

Before President Rouhani, Supreme Leader of the Islamic Revolution Ayatollah Seyed Ali Khamenei had warned late November that implementation of the extended Iran sanctions law for another 10 years would be equal to the violation of the nuclear agreement reached between Tehran and the six world powers in July 2015.

"There were a lot of debates about sanctions in the nuclear talks, but now they raise the issue of extending the sanctions in the US Congress and claim that these are not sanctions but renewal (of earlier sanctions)," the Supreme Leader said in a meeting with a group of Iranian Navy commanders and officials in Tehran on the occasion of the National Navy Day.

Ayatollah Khamenei pointed to the nuclear talks with the world powers, and said, "Initiating sanctions is no different from renewing them after their expiry date, as the latter is also (an instance of imposing) sanctions and a violation of the undertakings already taken up by the opposite side."