President Trump named Robert C. O’Brien as his new national security adviser Wednesday as he seeks to realign his staff and temper internal divisions following the turbulent reign of former national security adviser John Bolton.

The appointment of O’Brien solidifies the status of Secretary of State Mike Pompeo as the most influential foreign policy voice in the administration. Pompeo has known O’Brien for years and backed his ascension to the job after battling with Bolton over an array of policy issues on Afghanistan, Iran and North Korea, U.S. officials said.

O’Brien, who served as the nation’s top hostage negotiator, will now take on a far more daunting set of responsibilities as Trump’s fourth national security adviser. He takes over amid escalating tensions with Iran, a high-stakes trade war with China and concerns about whether he wields enough clout to forge consensus among the U.S. government’s competing egos and agencies.

But officials said they hoped his friendly demeanor and experience as a lawyer could bring more stability and collegiality to an often chaotic policymaking process going into the 2020 election.

“A major concern is cutting back on the drama,” said a senior U.S. official, who like others spoke on the condition of anonymity to speak about internal dynamics.

Trump praised his new pick in Los Angeles on Wednesday, saying O’Brien has “worked with me for quite a while now on hostages and we have a tremendous track record on hostages.”

O’Brien called it a “privilege” to take the adviser role and cited a number of “challenges” he would take on, including keeping America safe and rebuilding the military. On the heightened tensions with Iran, he said that “we’re looking at those issues now” and that he would advise the president privately on how to handle the situation.

Several officials said O’Brien would be less resistant to following the president’s orders than his predecessor, who opposed Trump’s negotiations with North Korea, withdrawal plans in Afghanistan and interest in engaging with Iranian leaders.

Although O’Brien is not known for sharing Bolton’s brand of rigid unilateralism, his past writings have emphasized the importance of U.S. alliances and American global leadership, a viewpoint that could clash with aspects of Trump’s “America First” agenda.

“Robert is strong on defense. He’ll be firm on China. He is a believer in American alliances. How similar is that to Bolton? I would leave it at that,” Kent Lucken, a longtime friend of O’Brien’s who worked with him on Mitt Romney’s presidential campaign, said in a phone interview.

A major question is whether O’Brien, whose personal history and rapport with the president has been limited, can formulate a coherent policy out of the president’s desires while managing his advisers at the Pentagon, State Department and Treasury.

“Without the power that results from deep relationship with the president, a reputation among the national security community or deep expertise in government, a weak national security adviser causes disorder,” warned John Gans, author of “White House Warriors,” a book on the history of the National Security Council.

As evidence, Gans pointed to the Iran-contra affair of the 1980s and the role of President Ronald Reagan’s national security advisers, Bud McFarlane and John Poindexter, whose standing was weaker than that of their colleagues in the Cabinet. “Although most suspect it was the result of ambitions, Iran-contra was really the result of bad management: neither McFarlane nor Poindexter had the power to get principals like Secretary of State George Shultz or Defense Secretary Caspar Weinberger to stop arguing, President Ronald Reagan to stick with a decision, or the strong-willed staff to take no for an answer,” he said.

Officials said a policy process that doesn’t create new competing factions would be welcome, particularly by acting White House chief of staff Mick Mulvaney, who observed the deep fissures between Bolton and senior Pentagon and State Department officials.

The position of national security adviser does not require Senate confirmation.

U.S. officials hope O’Brien's appointment will put an end to the rampant feuding between staffers for Pompeo and Bolton, who at times did not share information with each other out of suspicion that it would be used to undermine their positions ahead of a presidential policy decision.

Two people who worked closely with O’Brien described him as a savvy “political animal” who had cultivated a close relationship with Pompeo on hostage related issues and had long sought a promotion within the Trump administration. They said having an ally in the White House would further strengthen the position of Pompeo, who has been more careful than any of his departed colleagues in refusing to break with Trump publicly. Besides O’Brien, Pompeo also maintains close ties to CIA Director Gina Haspel, who worked for him when he led the spy agency, and Defense Secretary Mark T. Esper, his former classmate at the U.S. Military Academy.

Upon taking the job, O’Brien will become the highest-ranking Mormon in the U.S. government, an important development for a religious community that has shown some skepticism of Trump and will be a closely watched voting demographic in states such as Arizona. O’Brien converted from Catholicism in his 20s.

During his work for the Trump administration, O’Brien has divided his time between Los Angeles and Washington, maintaining his job at his law firm. According to his firm’s website, O’Brien has maintained a “robust” commercial litigation practice while serving as a special presidential envoy.

The dual roles have prompted criticism from some of the families of detained Americans who have pushed for a swift return of their relatives, U.S. officials said. On Wednesday, he also received praise from current and former colleagues, including a former official in the Barack Obama administration.

“All I have to say is that @robertcobrien is a really, really good person and that I wish him all the best in what will certainly be a challenging role,” tweeted Andrew Exum, a former deputy assistant secretary of defense for Middle East policy.

O’Brien has praised Trump for having “unparalleled success” in bringing home hostages, including the release of Pastor Andrew Brunson in Turkey and other Americans who were detained in the Middle East and South Asia.

But his appearance in Sweden in July to monitor the trial of U.S. rapper A$AP Rocky raised eyebrows as critics assailed Trump for what they viewed as an inappropriate intervention in an allied nation’s legal matters. Rocky was found guilty of assault this summer but received no additional jail time.

In Iran, O’Brien also has struggled to make progress in freeing U.S. detainees there, frustrating families seeking U.S. help.

O’Brien’s prior work with the State Department included serving as co-chairman of its Public-Private Partnership for Justice Reform in Afghanistan from 2007 to 2011. His law firm’s website notes that he served under two secretaries of state, Condoleezza Rice in the George W. Bush administration and Hillary Clinton in the Obama administration.

The announcement of O’Brien’s appointment came a day after Trump publicly named five finalists for the position, none of whom were well-known.

Bolton’s ouster last week ended a stormy tenure marked by widening rifts between an unorthodox president seeking a foreign policy victory and an irascible foreign policy hawk who had been deeply skeptical of much of the president’s agenda.

Bolton’s opposition to elements of Trump’s approach on North Korea, Iran and Afghanistan, among other issues, put him at odds with his boss and other advisers. Trump also largely blamed his third national security adviser for overselling the strength of Venezuela’s political opposition earlier this year.

Shane Harris and Anne Gearan contributed to this report.