President Trump will push NATO allies to fulfill key 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 benchmarks.
U.S. officials have portrayed rising tensions as "growing pains."
Observers reveal allies will obtain "report cards" to track their progress.
Various experts have warned of economic consequences if the demands are applied fully.