By Daniella Diaz and Dan Merica, CNN

(CNN) -- President Donald Trump on Saturday tweeted his support for protests taking place in Iran this weekend, writing, "The world is watching!"

In a pair of tweets, the President wrote: "The entire world understands that the good people of Iran want change, and, other than the vast military power of the United States, that Iran's people are what their leaders fear the most...."

Trump continued: "Oppressive regimes cannot endure forever, and the day will come when the Iranian people will face a choice. The world is watching!"

In the tweets, Trump posted videos of a speech he gave to the United Nations in September, in which he said, "The entire world understands that the good people of Iran want change."

The President's Twitter posts follow a White House statement making similar points, which he tweeted late Friday night.

Iran's government warned its citizens on Saturday against holding "illegal" public gatherings, following two days of rare anti-government protests which spread to a number of cities.

The protests -- described as the largest public display of discontent since the 2009 Green Movement in Iran -- have emerged against a backdrop of rising food and gasoline prices.

The unrest has prompted verbal sparring between Iran and the United States, with the White House and Trump on Friday urging Tehran to respect protesters' rights.

"There are many reports of peaceful protests by Iranian citizens fed up with the regime's corruption and its squandering of the nation's wealth to fund terrorism abroad," said White House press secretary Sarah Sanders. "The Iranian government should respect their people's rights, including their right to express themselves. The world is watching."

Trump subsequently tweeted the same message.

Trump campaigned for president with a hard-line stance on Iran, calling the country the "No. 1 terror state" during a debate with former Secretary of State Hillary Clinton. As President, he has tried to keep that hard-line stance and announced earlier this year that he plans to decertify the Iran nuclear agreement and push Congress to a new plan to deal with Iran's nuclear program.

By weighing in on the protests, though, Trump is wading into a tricky issue that has befuddled presidents ever since the Iranian Revolution of 1979 ended relations between Washington and Tehran.

Former President Barack Obama's response to protests in Iran in 2009 was timid initially, but grew more forceful. Although those protests eventually fizzled, Obama looked to deal with Iran by minting the nuclear agreement that Trump has tried to scrap.

Obama also looked to rekindle direct talks between Iran and the United States, including in 2013, when he became the first US president to speak with an Iranian president -- Hassan Rouhani in this case -- since 1979.

Former President George W. Bush dealt with Iran more forcefully, but to mixed results, labeling the country in 2002 as part of an "axis of evil" that included Iraq and North Korea. Bush's stance was the result of a softer approach taken by former President Bill Clinton, who worked at length to foster relations with former President Mohammad Khatami.

The difficult issue that American presidents have had to confront is how to support anti-government protests in Iran without dooming those same demonstrations by allowing Tehran to paint them as closely aligned with the United States, an allegation seen in Iran as a slight.

The-CNN-Wire

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