Trump has pulled out of an international agreement to constrict Iran's nuclear deal and restored sanctions.
United Nations: The White House promised Monday to keep exerting "maximum pressure" on Iran and said new sanctions were in the pipeline while insisting that the US was not seeking the overthrow of Tehran's clerical regime.
"As I have said repeatedly, regime change in Iran is not the administration's policy," national security advisor John Bolton told reporters as he previewed President Donald Trump's week at the United Nations General Assembly.
"We've imposed very stringent sanctions on Iran, more are coming, and what we expect from Iran is massive changes in their behaviour."
"And until that happens we will continue to exert what the president has called maximum pressure," he said.
As a private citizen, Bolton had advocated supporting Iran's armed opposition, a position reiterated recently by former New York mayor Rudy Giuliani, who serves as Trump's personal lawyer.
Trump, who has warm relations with Iranian rivals Saudi Arabia and Israel, has pulled the United States out of an international agreement to constrict Iran's nuclear program and instead has restored sanctions.
Iran's supreme leader Ayatollah Ali Khamenei has accused US allies Saudi Arabia and the United Arab Emirates of supporting Arab separatists who killed 24 people at a military parade last week in southwestern Iran.