U.S. President Donald Trump said Wednesday he plans to name hostage negotiator Robert O’Brien to be his new national security adviser.

Trump’s announcement about O’Brien comes a week after the departure of John Bolton from the national security adviser’s post, citing policy disagreements. Trump and Bolton offered differing views on whether the longtime Republican policy adviser resigned or was fired.

As the special presidential envoy for hostage affairs at the State Department, O’Brien worked closely with the families of American hostages and advised administration officials on hostage issues. He previously helped lead the department’s public-private partnership for justice reform in Afghanistan during the George W. Bush and Barack Obama administrations.

From 2008 through 2011, O’Brien was a presidentially appointed member of a government committee that advises on issues related to the trafficking of antiquities and other cultural items. In 2005, Bush nominated O’Brien to be U.S. Representative to the United Nations General Assembly, where he worked with Bolton. O’Brien was confirmed by the Senate.

He also was an adviser on the Republican presidential campaigns in the past of Ted Cruz, Mitt Romney and Scott Walker.

Earlier in his career, O’Brien was a senior legal officer for the UN Security Council commission that decided claims against Iraq that arose from the Gulf War. He was a major in the U.S. Army Reserve.

President Donald Trump and Robert O’Brien, just named as the new national security adviser, speak to the media at Los Angeles International Airport on Wednesday, not long after his appointment. (Evan Vucci/The Associated Press)

In his 2016 book, While America Slept, O’Brien detailed what he saw as some of the failures of U.S. foreign policy in recent years, particularly under the Obama administration.

Appearing alongside Trump early Wednesday afternoon, O’Brien said it is a “privilege to serve.”

“I look forward to working with the president to keep America safe and continue to rebuild our military and really get us back to a ‘peace through strength’ posture that will really keep the American people safe from the many challenges around the world today,” he said.

Republican senators such as Lindsey Graham of South Carolina, Ted Cruz of Texas and Marco Rubio of Florida took to social media to praise the hiring.

“His experience in hostage affairs, promoting rule of law in Afghanistan and the U.S. Army Reserve position him to provide valuable strategic and tactical advice to [the president] and our defense and diplomatic agencies,” said Rubio.

Presence in Sweden raised eyebrows

In his most recent role, O’Brien has worked to free Americans in Afghanistan, Syria and Libya. He was also dispatched by Trump to Stockholm this summer during the assault case faced by U.S. hip-hop artist A$AP Rocky, with the Swedish government taking pains to release a statement noting “this case is not in any way a “hostage affair.”

O’Brien defended his presence in Sweden to USA Today.

“When foreign governments hold American citizens it’s always appropriate,” he said.

“The president sent me. That also makes it appropriate,” he added.

O’Brien would represent Trump’s fourth permanent national security adviser, with the position not requiring Senate confirmation.

Trump’s first choice, Michael Flynn, was gone after three weeks for lying to the administration — and subsequently, the FBI — over contacts with Russia during the Trump transition to government.

Army Gen. H.R. McMaster succeeded Flynn and stayed in the role until April 2018.

Bolton’s hiring to succeed McMaster raised some eyebrows, given a world view seemingly ill suited to the president’s isolationist “America First” pronouncements.

Bolton had espoused hawkish foreign policy views and gave vociferous support for the Iraq War under George W. Bush. 

U.S. President Donald Trump said Tuesday via Twitter that he had fired national security adviser John Bolton and will name a replacement next week. Bolton lasted 17 months on the job, longer than any other. 2:28

Bolton’s exit continued the trend of dizzying pace of change in the administration, which has included the remaking of Trump’s foreign policy team.

Nikki Haley, U.S. ambassador to the United Nations and Secretary of Defence James Mattis also departed within the past year, with permanent replacements not firmly in place in the roles until many months later — Mark Esper as secretary of defence and former ambassador to Canada Kelly Craft to serve as ambassador at the UN, albeit with a classification downgrade from Haley’s cabinet-level role.

Secretary of State Mike Pompeo, meanwhile, has been on the job for 20 months, having succeeded Rex Tillerson, who also clashed with Trump.