The U.S. delegation had planned to visit the Brazilian capital and cast doubt on the integrity of the voting system before a presidential election this fall, officials said.
After threatening a “massive attack,” the president said his envoys were talking with Tehran but left open the possibility of a sharp military escalation.
Hours before addressing the White House press corps, the president endorsed using subpoenas against reporters in national security leak investigations.
The president will address a smaller, heavily secured gathering Friday as his administration intensifies its legal and rhetorical attacks on journalists.