He replaces Rex Tillerson, who was fired by President Donald Trump in March.
Mike Pompeo, US President's Donald Trump's pick to be secretary of state, vows diplomatic approach to Iran
With a history of provocative statements against Iran, Pompeo's nomination was seen as a sign that Trump's administration intends to rip up the accord.
Tillerson was also thought to have made a major concession to China when he publicly repeated Beijing's rhetoric about the Sino-US relationship during his first trip to the country.
President Donald Trump's sacking of Secretary of State Rex Tillerson could sound the death knell for the Iran nuclear deal and further strain US ties with key European allies.
Russia issued a mocking reaction to the surprise sacking of Rex Tillerson as Secretary of State, with a foreign ministry spokeswoman asking if the finger of blame was already being pointed at Moscow.
A top State Department official says President Donald Trump never explained to ousted Secretary of State Rex Tillerson the reason why he was fired.
The United States agreed with its ally Britain on Tuesday that Russia was probably behind an attempt to poison a former double agent, saying the perpetrators should face punishment.
Tillerson's comments came after President Trump agreed to a historic meeting with Kim, the first ever between a US president and a North Korean leader.
Tillerson said the signals from Pyongyang may be positive but stressed negotiations with Kim Jong Un's regime were not going to happen soon.
To expedite the move, the US will not build a new structure, but will instead convert an existing consular building in the Arnona neighbourhood of West Jerusalem into the new US mission.
The United States has mobilized the world community to impose stringent economic and diplomatic sanctions on Kim Jong-un's regime to halt its nuclear drive.
Asked if he wants Tillerson to remain in his post, President Donald Trump said only that 'Rex is here' at the White House.
U.S. officials and individuals familiar with White House plans have spoken about the possibility of a broad shakeup in President Donald Trump's national security team.
US Secretary of State Rex Tillerson today criticised Russia for often employing "malicious tactics" to not only weaken their confidence but also to undermine political and economic successes.
Tillerson's visit comes as global outrage builds over an army clampdown that has driven more than 600,000 Rohingya out of the mainly Buddhist country since late August.