"Never ever threaten the United States again or you will suffer consequences the likes of which few throughout history have ever suffered before", the president wrote, entirely in capital letters with the exception of the "greeting" to President Hassan Rouhani.
Trump responded with a tweet that warned: "NEVER EVER THREATEN THE UNITED STATES AGAIN OR YOU WILL SUFFER CONSEQUENCES THE LIKE OF WHICH FEW THROUGHOUT HISTORY HAVE EVER SUFFERED BEFORE".
The current and former officials said the campaign paints Iranian leaders in a harsh light, at times using information that is exaggerated or contradicts other official pronouncements, including comments by previous administrations.
The offensive is meant to work in concert with severe economic sanctions that Washington plans to reimpose in the coming months, including on Tehran's oil exports, its principal revenue generator.
"The idea that problems can be resolved through negotiations or relations with the United States is a major error", he added.
Although the Trump administration claims it only seeks "behavior change" in Iran, its pressure campaign clearly aims at regime change.
Mark Dubowitz, head of the Foundation for Defense of Democracies and a leading critic of Iran and the 2015 nuclear deal, called Pompeo's remarks a "powerful indictment of a corrupt and repressive regime", and suggested that US support will help lead to the demise of the theocratic government.More news: Bucks forward Christian Wood named to All-NBA summer league first team
Pompeo talked about increasing the media outreach to the Iranian people.
"There's more to come", Pompeo said.
Reuters reported on Sunday that high-ranking Iranian government officials are concerned that Trump may be contemplating an invasion of their country - a move which National Security Advisor John Bolton has advocated in the past.
"Iran's oil exports could fall by as much as two-thirds by the end of the year because of new US sanctions, putting oil markets under huge strain amid supply outages elsewhere", Reuters noted.
"The United States condemns the oppression levied on the Iranian people by those who rule unjustly", he said. Some experts say Kim is using diplomacy as a way to win outside concessions and weaken US -led worldwide sanctions.
FILE PHOTO: U.S. President Donald Trump speaks about his summit meeting with Russian President Vladimir Putin as he begins a meeting with members of the U.S. Congress at the White House in Washington, July 17, 2018.
It is unclear whether the European Union can salvage the nuclear deal without the support of the United State, which is taking a hardline approach on the Gulf nation.
Pompeo has expressed support for the protesters on several occasions, including in a June 21 tweet.
This will ensure that "ordinary Iranians inside Iran and around the globe can know that America stands with them", he said.