The outlet noted that while aides and other officials are expected to join in the meeting afterward, there will be a portion of time that is undocumented, leaving open the question of what agreements might be reached privately between the two leaders.
Expected to be addressed during the summit are Russian election meddling, Syria and nuclear weapons.
The two leaders will meet in Helsinki on July 16. The meeting will be the first formal summit between Trump and Putin.
The presidents also spoke for about an hour alone during a dinner at the summit last year, with Trump relying on the Russian leader's translator.
The idea that Trump would talk with Putin alone is troubling to some, as the president remains under investigation for potential collusion with Russia during the 2016 election.
White House national security adviser John Bolton said recently that the subject was raised during his preliminary meetings with his Russian counterparts ahead of the July summit, also indicating the issue would arise when Trump and Putin meet as well.