It was not clear whether Trump meant Washington actually has intelligence of such a plan.
The death is believed to have occurred before the recent outbreak of the coronavirus.
Iran is one of the hardest-hit countries in the world by the new virus.
Iran has granted a medical furlough to a U.S. Navy veteran imprisoned for more than a year.
The Navy demonstrated it can coordinate with AC-130 gunships for maritime strike against potential hostile surface ships.
The U.S. is also in the process of moving Patriot anti-missile batteries into Iraq.
The Pentagon said it would keep two aircraft carrier task forces in the Gulf region after carrying out strikes in Iraq.
One U.S. official said multiple strikes targeted Kataib Hezbollah weapons facilities inside Iraq.
The U.S. and Britain vowed to hold accountable those responsible for an attack in Iraq that killed three troops.
Officials said the strike also killed Abu Mahdi al-Muhandis, the deputy commander of Iran-backed militias known as the...