Many Iranians have taken to social media to criticize U.S. President Donald Trump for taking a harder line on the Islamic republic and refusing to certify the 2015 landmark nuclear agreement with Iran, which is believed to enjoy significant support in the country.

In his comments, Trump called Iran a "rogue" and "fanatical" regime and said that the country had failed to live up to the "spirit" of the nuclear deal, under which Iran agreed to limit its controversial nuclear activities in exchange for sanctions relief.

Many Iranians expressed support for the deal and the removal of sanctions by taking to the streets when it was signed and celebrating.

Trump's decision to decertify the deal and his outreach effort to Iranians was met with anger.

"We hope that these new measures directed at the Iranian dictatorship will compel the government to reevaluate its pursuit of terror at the expense of its people," Trump said in his speech, which expressed solidarity with the Iranians.

"Trump's outreach to Iranian public is a joke, Iranians know well how unreasonable and unfounded his policy to Iran is. They reject Trump," women's rights activist Sussan Tahmasebi tweeted.

"Trump's comments were not only against Iran, they were against a diplomatic move to resolve a global issue," said former Iranian lawmaker Jamileh Kadivar, who lives outside the country.

Mostafa Tajzadeh, a reformist politician critical of the Islamic establishment who was jailed in Iran for several years, was among those criticizing Trump's speech.

"One nation, one message: No to #Trump. We're all in this together," wrote Tajzadeh on Twitter a day after Trump announced his Iran strategy.

"The [nuclear deal] had brought us some peace of mind. This Trump's move brings us concern. Why is playing with the future of our children," wrote a woman on Facebook.

"Trump: #Iran blah blah blah... sorry I couldn't derail this deal, dear Senators do this for me if you can," tweeted Tehran-based journalist Sadegh Ghorbani, who works for hard-line news outlets.

Some were using hashtags that said #nevertrustUSA and #IranKeepspromises in their reactions to Trump's speech, in which he announced his new Iran strategy that includes new sanctions against Iran's Islamic Revolutionary Guards Corps (IRGC).

"The irony is that a country that has a record of attacking other countries and launching coups has a terrorist scale in hand," Leila Samani tweeted.

"While the international community says Iran is abiding by the deal, the U.S. says otherwise. Never trust a bully," Farid Sobhani tweeted.

"Trump says Iran's government attacked the U.S. in a way as if it was Iran that destroyed a U.S. plane with 290 passengers," a Twitter user said in a reference to the downing of an Iran Air flight that was shot down by the U.S. Navy in July 1988, killing all passengers on board.

However, some expressed support for Trump's strategy.

"America should sanction Iranian [leaders] and whoever works with them," a reader commented on the website of RFE/RL's Radio Farda. "The Iranian regime does not have public support," the reader added.

Other users said the new move by the Treasury Department to sanction the IRGC as a terrorist organization was a good thing.​

"We agree with the designation of Iran Revolutionary Guards as a terrorist organization," tweeted user Parinaz Etesam with the #hashtag #IRGCByeBye.

"Viva President Trump," another reader said. "He sanctioned the IRGC, the murderers of hundreds of young Iranians, the number one enemy of freedom in Iran," the reader added.

"I'm glad Trump differentiated between the people and the [Iranian] regime," a comment on Radio Farda website said.

'Arabian Gulf'

Many Iranians on social media were up in arms over Trump's use of the term "Arabian Gulf" to refer to the body of water known historically as the Persian Gulf. Iranians insist that it be referred to as the Persian Gulf, taking Arabian Gulf as an insult.

"It always was Persian and it always stays Persian," a tweet said with a map saying "Persian Gulf."

"Someone teach @RealDonaldTrump geography lessons!," another user said while adding: "It's #PersianGulf."

Iranian users took to Trump's Instagram page to voice their protest. Around two hours after the post went online, it had received 400,000 comments, most of which regarding the Arabian/Persian Gulf issue.