California Governor Gavin Newsom said on Tuesday that US President Donald Trump's comments about a possible Iranian attack on Los Angeles or San Diego were "disgusting and disqualifying".
Clips have spread on social media of Mr Trump at a rally in Nebraska on Monday night, in which he appeared to encourage Iran to "take out" the major cities in the Democratic-leaning state.
"Donald Trump’s remarks were dangerous – if not treasonous – putting a target on two of our biggest cities and one of America’s largest naval hubs," Mr Newsom said in a post on X.
"I am directing the State Threat Assessment Centre to actively monitor the situation in the event that foreign actors interpret the President’s remarks as an invitation to target California."
The FBI warned this year that Iran could attempt to strike California in a drone attack.
"The role of a president is to protect the country, not to actively threaten it and encourage attacks on American lives," Los Angeles Mayor Karen Bass wrote on X.
But the White House said that Mr Trump's comments were taken out of context, and were actually about petrol prices.
"The media freak-out over President Trump’s comments is not rooted in reality," White House spokesman Steven Cheung said. "He was clearly stating US cities would have been threatened if a nuclear Iran hadn't been stopped. America is safer because of the President."
During the rally, Mr Trump said that a "tremendous victory" in the coming elections would verify all of the actions his administration has taken.
He and his Republicans are facing increasing pressure before the midterm elections in November, as petrol prices and those of other necessities remain high, and the war with Iran, although muted, continues.
"And again, remember, with the war, it's just artificial. It's a little bit high. It's a small price to pay for keeping the world safe, keeping our country safe. They can take out a city. Let them take out Los Angeles, let them take out San Diego," Mr Trump said to applause and cheers.
"This is a very small price to pay and it's going to be over very soon. It's essentially almost over with."
Mr Trump and Mr Newsom have been publicly critical of each other's policies. Last year, Mr Trump sent the National Guard to Los Angeles to control immigration-related protests. In response, Mr Newsom filed a lawsuit against the administration.
Mr Newsom also claimed in June that Mr Trump ordered a criminal investigation into him and his wife.
