At least 544 people have died in Iran amid ongoing protests, as the U.S. signals potential military action against the Islamic Republic, President Donald Trump said on Sunday.

Trump told reporters aboard Air Force One that Iran has indicated a willingness to enter negotiations, even as his administration considers “very robust options,” including cyber operations and direct strikes by the U.S. or Israel. Two officials familiar with internal deliberations confirmed the range of measures under discussion, speaking on condition of anonymity due to the sensitivity of the matter.

“The military is examining the situation, and we are contemplating some very robust options,” Trump said. Asked about the threat of Iranian retaliation, he added: “If they proceed with that, we will strike them at levels they have never experienced before.”

The president also suggested talks with Tehran may be possible, though action could be taken beforehand given the rising death toll and continued arrests of protesters. “I believe they are weary of being mistreated by the United States,” Trump said. “Iran is seeking to negotiate.”