TEHRAN (Dispatches) -- Iran will react sharply to any U.S. move against the nuclear deal with global powers, Foreign Minister Muhammad Javad Zarif told the Iranian parliament Wednesday, according to a parliamentarian who attended the session.
The comments were the latest in a series of warnings by Iranian officials, showing a united front among all political groups as U.S. President Donald Trump prepares to harden policy towards Tehran this week.
"In the closed session Zarif emphasized that if the Americans take any steps against the nuclear deal that the Islamic Republic of Iran will give them a more crushing response,” Shahbaz Hassanpour, a lawmaker representing the city of Sirjan, told the Islamic Republic News Agency (IRNA).
Another lawmaker, Behrouz Nemati, said the foreign minister discussed specific steps Trump and the U.S. Congress might take, and Iran’s plans for reciprocal action to each anticipated U.S. move. Nemati did not say what actions Zarif had described.
Trump is expected this week to "decertify” the landmark 2015 deal under which Iran agreed with global powers to accept curbs on its nuclear program in return for the lifting of sanctions.
"Decertification” would not by itself withdraw the United States from the agreement, but would pass that decision on to Congress, requiring lawmakers to decide within 60 days whether to re-impose sanctions.
Trump is also expected to declare Iran’s Islamic Revolution Guards Corps (IRGC) a terrorist organization.  
The threat of increased U.S. pressure has been met by a united front of criticism from within Iran, with members of the faction that seeks greater interaction with the West showing their support for the IRGC.
Zarif on Tuesday met with IRGC chief Major General Muhammad Ali Jafari.
During the meeting with Zarif, parliament members expressed their support for the Guards, Hassanpour said. Zarif also noted during the session that European countries will continue backing the nuclear deal regardless of what actions the U.S may take, Hassanpour told IRNA.
Rouhani: IRGC in the Heart of People
Meanwhile, President Hassan Rouhani gave a full-throated defense of the IRGC on Wednesday during a cabinet meeting shown on state television, saying U.S. action against the Guards would be a "mistake beyond mistakes.”
"They think that the Guards are a military entity. The Revolutionary Guards are not a military entity. They’re in the heart of the people. The Revolutionary Guards, in all the days of danger, have defended our national interests,” he said.
"We’re one society. We’re Iran. There are no differences between different factions in confronting the plots of our enemies,” he added.
Rouhani said, "Today, the president of America has created conditions where Iran is more united than ever. Today, those who oppose the nuclear deal and those who support it are side by side. We all have one voice.”
He said Trump was "clearly upset" over the Guards' military successes against Daesh in Syria and Iraq.
"OK, if you want to keep Daesh in this region for 20 years and use it as a tool, then OK, it is your right to be angry with the Revolutionary Guards. Because the Revolutionary Guards, by their planning, and support for the nations of Iraq, Syria and Lebanon have humiliated Daesh," Rouhani said.
The president also said Trump he was opposing "the whole world" by trying to abandon the nuclear agreement.
"If the U.S. wants to take a hostile position regarding an international agreement which is approved by the UN Security Council ... they will oppose not just Iran but the whole world," Rouhani said.
"It will be absolutely clear which is the lawless government. It will be clear which country is respected by the nations of the world and global public opinion," he added.
Other parties to the deal - Britain, France, Germany, China, Russia and the European Union - have all voiced staunch support for it, saying Iran has stuck to its commitments.
The nuclear deal "is a test for all governments," Rouhani said. "Whenever we have committed ourselves, we have stood by our commitments to the end. This is an honor for us."
May: UK Committed to Iran Deal
 
Prime Minister Theresa May on Tuesday reaffirmed Britain's commitment to the Iran nuclear deal in a telephone conversation with Trump.
"The (prime minister) reaffirmed the UK's strong commitment to the deal alongside our European partners, saying it was vitally important for regional security," said a statement from May's office following the call on Tuesday evening.
"(The prime minister) stressed that it was important that the deal was carefully monitored and properly enforced."
In a separate statement, Britain's Foreign Office said Iran had upheld its nuclear commitments, adding to international pressure on Trump not to jeopardize security in the region.
The nuclear agreement "was the culmination of 13 years of painstaking diplomacy and has increased security, both in the region and in the UK. It is these security implications that we continue to encourage the U.S. to consider," Foreign Secretary Boris Johnson said.
Johnson spoke by telephone with U.S. Secretary of State Rex Tillerson and Foreign Minister Zarif on Tuesday and was on Wednesday to meet the head of Iran's nuclear agency Ali Akbar Salehi in London.
The White House said Trump would make an announcement later this week on an "overall Iran strategy," including whether to "decertify” the nuclear deal.