Mike Pompeo has been sworn in as the new U.S. secretary of state, promising "tough diplomacy" to advance U.S. interests.

Pompeo, a former director of the CIA, took the oath of office at a State Department ceremony on May 2 attended by President Donald Trump.

"We will employ tough diplomacy when necessary to put the interests of the American people first," he told an audience of State Department employees.

"We've put hurt on the [Islamic State] caliphate in Iraq and Syria. We've done so by great diplomatic work," he said.

"We are confronting all types of Iranian hostility and are deciding on the next steps" for the Iranian nuclear deal, which he called flawed.

"We have imposed real consequences on Russia for its acts of aggression; and we will soon move our embassy in Israel to Jerusalem, years ahead of schedule," he said.

A former Republican congressman, Pompeo is known for having hawkish views on major foreign-policy issues, including Russia, Iran, and North Korea.

He replaces Rex Tillerson, the ExxonMobil chief executive who clashed repeatedly with Trump and who was unceremoniously fired by Trump last month.