President Donald Trump named U.S. hostage negotiator Robert O'Brien as his new national security adviser a week after firing John Bolton, who reportedly clashed with the president on a number of foreign policy matters, Reuters reported.
The president tweeted his pick for national security adviser Sept. 18, saying he has "worked long and hard" with O'Brien, who "will do a great job" at his new role.
O'Brien will be the fourth national security adviser under Trump and is currently the special envoy for hostage affairs at the U.S. State Department.
Trump fired Bolton after disagreements over how to handle North Korea, Iran, Afghanistan, Russia and Venezuela, according to Reuters.
O'Brien, an attorney from Los Angeles, has been involved in several Republican presidential campaigns as a foreign policy adviser, and has served in the State Department in different capacities, including a 2005 stint as an alternative representative to the U.N. General Assembly.
Most recently, he was dispatched by Trump to Sweden for the court hearing of U.S. rapper A$AP Rocky, who was eventually convicted for assault but was not given jail time.
