U.S. National Security Adviser John Bolton, a hardliner on North Korea, will travel to Singapore as part of President Trump's entourage for the North Korea-U.S. summit.
Bloomberg reports that White House Chief of Staff John Kelly and Secretary of State Mike Pompeo will also accompany Trump to Singapore.
Defense Secretary James Mattis will not be part of the delegation.
Bolton's inclusion comes as officials at the State Department believe he controversially suggested North Korea's denuclearization should follow "the Libya model" to disrupt talks with the regime.
CNN reports that the officials believe Bolton tried to (quote) 'blow up' the North Korea talks,... and that there has been "considerable tension" between Bolton and Pompeo,... enough to even prompt Pompeo to physically confront Bolton.
The National Security Council denies there was any such confrontation.