With the clerical establishment facing the biggest demonstrations since 2022, Trump has repeatedly threatened to intervene if force is used against protesters.
According to its latest figures - from activists inside and outside Iran - US-based rights group HRANA said it had verified the deaths of 490 protesters and 48 security personnel, with more than 10,600 people arrested in two weeks of unrest.
Iranian authorities have not given an official toll and Reuters was unable to independently verify the tolls.
Trump was to be briefed by his officials on Tuesday on options over Iran including military strikes, using secret cyber weapons, widening sanctions and providing online help to anti-government sources, the Wall Street Journal said on Sunday.
Iranian parliament Speaker Mohammad Baqer Qalibaf warned the US against "a miscalculation".
"Let us be clear: in the case of an attack on Iran, the occupied territories (Israel) as well as all US bases and ships will be our legitimate target," said Qalibaf, a former commander in Iran's elite Revolutionary Guards.
The protests began on December 28 in response to soaring prices, before turning against the clerical rulers who have governed since the 1979 Islamic Revolution.
Iranian authorities accuse foreign powers of fomenting trouble and called for a country-wide rally on Monday to condemn "terrorist actions led by the United States and Israel" in Iran, state media reported.
The flow of information from Iran has been hampered by an internet blackout since Thursday.
Footage posted on social media on Saturday from Tehran showed large crowds marching along a street at night, clapping and chanting.
The crowd "has no end nor beginning," a man is heard saying.
In footage from the northeastern city of Mashhad, smoke can be seen billowing into the night sky from fires in the street, masked protesters, and a road strewn with debris, another video showed.
Reuters verified the locations.
State TV showed dozens of body bags on the ground at the Tehran coroner's office, saying the dead were victims of events caused by "armed terrorists," as well as footage of loved ones gathered outside the Kahrizak Forensic Medical Centre in Tehran waiting to identify bodies.
Israel and Iran fought a 12-day war in June last year, which the US briefly joined by attacking key nuclear installations.
Iran retaliated by firing missiles at Israel and a US air base in Qatar.
Iranian President Masoud Pezeshkian, in a TV interview, said Israel and the US were masterminding destabilisation and that Iran's enemies had brought in "terrorists ... who set mosques on fire .... attack banks, and public properties".
"Families, I ask you: do not allow your young children to join rioters and terrorists who behead people and kill others," he said, adding that the government was ready to listen to the people and to resolve economic problems.
Alan Eyre, a former US diplomat and Iran expert, thought it unlikely the protests would topple the establishment.
"I think it more likely that it puts these protests down eventually but emerges from the process far weaker," he told Reuters, noting that Iran's elite still appeared cohesive and there was no organised opposition.
Iranian state TV broadcast funeral processions in western cities such as Gachsaran and Yasuj for security personnel killed in protests.
Trump, posting on social media on Saturday, said: "Iran is looking at FREEDOM, perhaps like never before. The USA stands ready to help!!!".
Reza Pahlavi, the son of the Iranian shah who was overthrown in 1979, adopted a more moderate tone in a new message.
"I ask all of you to go to the main streets of the cities in groups with your friends and family members; along the way, do not separate from one another or from the crowds of people; and do not take side streets that could endanger your lives," Pahlavi said.
On Saturday, Pahlavi, who lives in exile in the United States, had called for strikes in the oil, gas and energy sectors and for demonstrators to occupy and control central squares in cities.
A critic wrote on X that Pahlavi's Saturday post urging the seizure of city centres puts demonstrators in danger.
Given the expected reaction of the trigger-happy authorities, the critic considered this approach irresponsible.
with DPA
