Matt Pottinger, National Security Council Senior Director for East Asia, arrive for the opening ceremony of the Belt and Road Forum in Beijing, Sunday, May 14, 2017.

U.S. President Donald Trump's national security advisor said on Sunday that White House Asia policy advisor Matt Pottinger would become his top deputy.

Robert O'Brien made the announcement on Air Force One as Trump flew from Ohio to New York, where the president will spend most of the week attending events related to the United Nations General Assembly.

Last Wednesday, Trump named O'Brien, a veteran foreign policy hand who had served as U.S. hostage negotiator, to replace John Bolton as national security advisor.

Trump and the hawkish Bolton had differences over foreign policy challenges such as Iran, Afghanistan and North Korea.

Pottinger is a former journalist and ex-U.S. Marine who has helped forge China and North Korea policy since Trump took office in January 2017.

"He's a team player," O'Brien said.

Pottinger played a key role in arranging Trump's summits with North Korean leader Kim Jong Un, a diplomatic engagement that has made little progress toward persuading Pyongyang to give up its nuclear weapons.