President Trump will press NATO allies to fulfill critical defense spending commitments at a summit in Turkey this week.
The pressure follows promises secured from member nations last year.
NATO's chief has requested that allies submit plausible plans to reach spending targets.
U.S. officials have described heightening tensions as "growing pains."
Analysts reveal allies will get "report cards" to track their progress.
Some observers have cautioned of fiscal consequences if the demands are enforced fully.