Bolton was grilled by reporters over his past comments about Russia.
President Donald Trump's national security adviser sharply criticized the Russian president in the past.
Beijing is keeping a close eye on which officials Washington will send.
North Korea threatened a "nuclear-to-nuclear showdown" after Vice President Mike Pence suggested Kim Jong Un could be overthrown.
President Donald Trump's decision came shortly after a top North Korean diplomat insulted the vice president, but there may be more at play.
He also contradicted his national security adviser John Bolton.
The national security adviser said he couldn't rule it out.
Who is in charge of the national security policy of the United States?
National security adviser John Bolton's arrival at the White House increases the chances of a harder line on Iran.
Fox News is Trump's propaganda arm—and both will do anything to boost ratings.
The selection of John Bolton as national security adviser has increased fears of a conflict with North Korea.
President Donald Trump and North Korean supreme leader Kim Jong Un's meeting could signal a diplomatic victory, if nuclear war doesn't break out first.
Experts say John Bolton's appointment as national security adviser could lead to the next major U.S. war 15 years after he supported the invasion of Iraq.
Bolton has said that the two-state solution, for which the international community advocates, is dead.
The president's staff shakeup continued Thursday with the selection of John Bolton as national security adviser.
Bolton is a notorious foreign policy hawk.