US President Donald Trump has said Iran proposed negotiations following his warning of possible military action against the Islamic Republic, as an ongoing crackdown on anti-government demonstrations has reportedly left hundreds dead.

Speaking to reporters aboard Air Force One late Sunday, Trump said his administration was working to arrange a meeting with Tehran but warned that events on the ground could force the United States to act sooner.

“A meeting is being arranged, but we may have to take action because of what’s happening before that meeting. Iran reached out—they want to negotiate,” Trump said.

Iranian authorities did not immediately respond to Trump’s remarks. In earlier statements, Tehran warned that the U.S. military and Israel would be considered “legitimate targets” if Washington uses force in response to the protests.

According to the U.S.-based Human Rights Activists News Agency, which has previously provided reliable data during periods of unrest in Iran, at least 544 people have been killed so far. The group said the dead include 496 protesters and 48 members of the security forces. More than 10,600 people have reportedly been detained during the past two weeks of demonstrations.

Assessing the scale of the unrest from outside Iran has become increasingly difficult, as internet services remain disrupted and phone lines have been cut. Iranian authorities have yet to release official nationwide casualty figures.