President Donald Trump’s attendance at the NATO summit in Brussels this week was defined by a combination of antagonism and spectacle, leaving allies alienated and confused. After lobbing insults at Germany and lecturing allies on their levels of defense spending, Trump closed out the summit dedicated to European security, by casting doubt about his position on key issues such as Crimea’s status and whether the U.S. would continue military exercises in the Baltics.

Leaving the alliance more divided and uncertain than it has been in its 70-year history, Trump now heads to a bilateral meeting in Helsinki on Monday with Russian President Vladimir Putin. The agenda is expected to cover a series of controversial issues including Syria, Ukraine, and Russia’s election meddling. However, there is one issue that should be a red flag if it’s at all a part of the discussion: sanctions relief for Russia.