By Lili Bayer and Andrew GrayBRUSSELS, July 6 (Reuters) - NATO leaders will gather in Ankara for a summit on Tuesday and Wednesday, amid pressure from President Donald Trump for Europe to step up defence spending and following months of transatlantic friction over the Iran warand Greenland.The U.S.. president's frequent criticism of NATO, along with announced troop withdrawals from Europe and a six-month review of the U.S. military presence on the continent, has fuelled uncertainty within the alliance.Here is what you need to know about the summit:

By Lili BayerBRUSSELS, July 3 (Reuters) - NATO leaders gathering for a summit in Ankara on July 7-8 will discuss a host of challenges facing the alliance, from Europe taking on…

NATO leaders convene in Ankara facing critical challenges: maintaining US commitment amid Trump's skepticism, Europe increasing its security role, and boosting defense spending.…