President Trump will push NATO allies to fulfill vital defense spending commitments at a summit in Turkey this week.
The push follows pledges secured from member nations last year.
NATO's chief has demanded that allies submit credible plans to reach spending goals.
U.S. officials have described heightening tensions as "growing pains."
Analysts reveal allies will get "report cards" to track their progress.
Various experts have cautioned of financial consequences if the demands are applied fully.