President Donald Trump has decided to fire John Bolton from his position as National Security Advisor. The president’s decision was announced via Twitter late Tuesday morning.

“I informed John Bolton last night that his services are no longer needed at the White House. I disagreed strongly with many of his suggestions, as did others in the Administration, and therefore I asked John for his resignation, which was given to me this morning. I thank John very much for his service. I will be naming a new National Security Advisor next week.” Trump tweeted.

Bolton was the third person to hold the role of Trump’s national security advisor since he took office in January of 2017. The decision to relieve Bolton comes amid heightened tensions with a number of America’s longstanding diplomatic opponents, including ongoing concerns about Iran‘s nuclear program. Bolton, as has been noted repeatedly since taking office, has long held a hard and even aggressive position toward Iran.

Trump recently announced a willingness to meet with President Hassan Rouhani of Iran, provided the circumstances were appropriate. He even offered to extend short-term financing to the Iranian government as part of a what some might call an olive branch amid concerns about Iranian aggression in the Strait of Hormuz — an essential waterway that provide access to the Persian Gulf. Thus far, Iranian officials have dismissed Trump’s offer.

Unconfirmed reports from within the White House have long suggested that the president was concerned that Bolton wanted to steer the nation toward another war. After Trump campaigned on the concept of scaling down America’s oversees combat operations, his national security advisor reportedly favored the idea of military intervention in Iran following the downing of a U.S. Navy drone flying near Iranian airspace. When Trump went to meet with North Korea’s Supreme Leader Kim Jong Un in June, a man Trump has been cordial to publicly while Bolton has remained critical, Bolton chose not to accompany the president on the trip.

“If it was up to John, we’d be in four wars now,” the New York Times reported that Trump once said to an unnamed White House official.

Thus far, there has been no announcement regarding who Bolton’s replacement will be.