Iranian President Hassan Rohani hailed European officials’ presence at his swearing-in ceremony, saying it showed the Continent was determined to expand ties with Tehran.
Rohani on August 5 also attacked the United States, accusing it of trying to undermine a 2015 nuclear accord and warning President Donald Trump that he was "ripping up" his political life with his policies toward Tehran.
Rohani, 68, a relative moderate cleric who won re-election on May 19, was sworn in for his second term at a lavish ceremony attended by more than 100 foreign dignitaries.
In a televised addressed, Rohani promised that Iran would pursue a "path of co-existence and interaction with the world."
But he took shots at Trump, who he claimed is violating terms of the 2015 nuclear agreement, which led to the easing of sanctions against Iran in return for curbs on its nuclear program.
"Those who want to tear up the nuclear deal should know that they will be ripping up their own political life," he said in remarks directed at Trump.
The United States has long said that Tehran is a major sponsor of terrorism and undermines stability in the region. Defense Secretary Jim Mattis has also called Iran "the single biggest state sponsor of terrorism in the world."
On August 3, the United States and three of its European allies urged the United Nations to send "a clear message to Iran" in response to its July 27 launch of a satellite-carrying rocket that the Western powers said had a "destabilizing effect in the region."
U.S. officials said that particular type of technology is inherently designed to carry a nuclear payload, and the Pentagon said it could be used to develop intercontinental ballistic missiles (ICBM).
The U.S. Senate voted in late July to impose new sanctions on Iran over its missiles program and human rights issues, and Trump signed the measure on August 3.
Among the dignitaries attending Rohani's swearing-in were officials from Europe, including French Foreign Minister Jean-Yves Le Drian, German Foreign Affairs Minister Michael Roth, and British Minister of State for the Middle East and North Africa Alistair Burt.
Russian Deputy Prime Minister Dmitry Rogozin, Iraqi President Fuad Masum, Afghan President Ashraf Ghani, and Zimbabwean President Robert Mugabe also attended the ceremony.
Ahead of the ceremony, Rohani met with European foreign policy chief Federica Mogherini.
Security was increased in Tehran to the highest level, police said, two months after gunmen linked to the Islamic State (IS) militant group attacked parliament and the shrine of Ayatollah Ruhollah Khomeini, killing 17 people.
The pragmatist Rohani was first elected in 2013 with nearly 51 percent of the vote. He won 57 percent in the May election after promising to build bridges with the outside world and create more jobs.
Analysts say Rohani may have difficulties in his attempts to open up the country to the West given that presidential powers are subordinate to those of the unelected Supreme Leader Ayatollah Ali Khamenei and because of Trump's hard-line policies toward Tehran.