Donald Trump has pledged "great support" for the people of Iran from the US over street protests currently taking place across the country.

The tweet, which said support would come at "the appropriate time" as Iranians look to "take back their corrupt government", replaced an earlier deleted tweet which called Iran a "corrupt and poorly run" country which its people were in a "fight" to take back.

“Such respect for the people of Iran as they try to take back their corrupt government. You will see great support from the United States at the appropriate time!” the full Twitter post reads.

Iran has endured its biggest unrest in nearly a decade after protests erupted late last month.

Seemingly spontaneous demonstrations erupted in Iran's second largest city, Mashhad, on December 28, and have since spread across the country.

The protests, according to reports, are stronger in the provinces than they are in Tehran, and are composed predominantly of working class people under the age of 25 who are angry that the benefits from the partial lifting of sanctions following the 2015 nuclear deal with the United States haven't been spread evenly amongst the population.

Iran protests – in pictures Show all 11 1 /11 Iran protests – in pictures Iran protests – in pictures University students at an anti-government protest inside Tehran University, 30 December 2017 AP Iran protests – in pictures A university student at a protest inside Tehran University while a smoke grenade is thrown by anti-riot Iranian police, 30 December 2017 AP Iran protests – in pictures University students at a protest inside Tehran University, 30 December 2017 AP Iran protests – in pictures University students run away from the police during an anti-government protest inside Tehran University, 30 December 2017 AP Iran protests – in pictures An image grab taken from a handout video released by Iran's Mehr News agency reportedly shows a group of men pulling at a fence in a street in Tehran, 30 December 2017 AFP/Getty Iran protests – in pictures Demonstrators gather to protest in Tehran, 30 December 2017 AP Iran protests – in pictures Iranians chant slogans as they march in support of the government near the Imam Khomeini grand mosque in Tehran, 30 December 2017 AFP/Getty Iran protests – in pictures Iranians chant slogans as they march in support of the government near the Imam Khomeini grand mosque in Tehran, December 30 2017 Iran protests – in pictures Iranian clerics take part during a state-organized rally against anti-government protests in the country, in the holy city of Qom, south west Iran, 3 January 2018 EPA Iran protests – in pictures In this photo provided by the Iranian Students' News Agency, a clergyman takes a picture of a pro-government demonstration in the southwestern city of Ahvaz, Iran, 3 January 2018 ISNA via AP Iran protests – in pictures Pro-government demonstrators gather at the Massoumeh shrine in Iran's holy city of Qom, some 130 kilometres south of Tehran, 3 January 2018 AFP/Getty

Mr Trump, for his part, has been a frequent critic of that nuclear deal, which was negotiated by his predecessor, President Barack Obama. He has so far stopped short of eliminating the understanding between the two countries outright, but refused to recertify the deal last year, opening up the possibility that Congress could take action and reimpose sanctions that would break the agreement. His decision not to recertify when the October 15 legal deadline arrived came in spite of findings by international inspectors who said that Iran has so-far complied with its obligations under the deal, which includes dismantling centrifuges, and limiting uranium enrichment.

But, the protests come at a particularly vulnerable time for that deal's continued existence.

Observers note that Mr Trump could potentially seize upon the unrest in Iran to follow through with his campaign promise to tear up the deal, even though some of his top advisers have warned him that doing so could embolden Iranian hard-liners to restart their pursuit of nuclear arms, while simultaneously isolating the United States on the issue.

Mr Trump will be forced this month to make a decision on the deal, and whether to waive the sanctions that the agreement has lifted. That is, unless Congress manages to forge its own legislation to address the issue, proving to the President that it has been strengthened while simultaneously garnering enough support in the Senate to meet a 60-vote threshold that would require some Democrats to come on board.

Some Republican hawks are pushing for further restrictions on Iran in light of the protests, including targeting short-range missiles that were not a part of the original deal because they are not nuclear-related. Others see the protests as a potential opportunity to reinforce existing laws targeting Iran, including the Global Magnitsky Act, which was passed in 2016 and extended a statute targeting human rights abusers in Russia to violators internationally.

Iran has repeatedly indicated that they would not renegotiate the nuclear deal.

At least 20 people have been killed in the protests, and at least 450 have been arrested in just Tehran, according to the Associated Press.

While Trump administration officials have so-far been careful in their statements surrounding the protests, hesitant to play into Iranian government propaganda that would allow the government to portray the issue as a conflict between outside forces and Tehran, experts have cautioned that reimposing sanctions could allow the government to do just that.