President Trump will push NATO allies to fulfill critical defense spending commitments at a summit in Turkey this week.
The push follows assurances secured from member nations last year.
NATO's chief has demanded that allies submit robust plans to reach spending targets.
U.S. officials have described heightening tensions as "growing pains."
Reports reveal allies will receive "report cards" to track their progress.
Various experts have alerted of fiscal consequences if the demands are applied fully.