Trump's surprise demand came after he clashed with Chancellor Angela Merkel, calling Germany a "captive" of Russia
Trump openly questioned the value of the generations-old alliance ahead of the meeting and linked US spending for Europe's defence with America's trade deficit with the world's largest trading bloc
Then there's the long shadow cast by Vladimir Putin, and fears in some allied capitals at what Trump might offer the Russian leader at their summit in Helsinki next Monday
Trump made no mention of his commitment to NATO's Article 5 collective defence guarantee
He also thanked the Chancellor for her leadership in supporting Nato and its efforts in Afghanistan
The meeting with Merkel will also allow Trump to discuss peace efforts in Ukraine
NATO had decided to freeze its relations after Russia illegally annexed the Crimean peninsula
First such contact since NATO suspended dialogue with Russia in 2014 after Crimea's annexation
Russia says the time when the West called the shots was over while Nato was a relic of the Cold War
To spend at least 2% of their GDP on defence
He also sought to reassure allies about President Donald Trump's commitment to the alliance
Trump accepted Merkel's invitation to attend the G20 Summit of developed and emerging countries
Hearkening back to language not employed in the United States since the 1930s
Trump has often indicated that as President he might not be committed to NATO
The US President-elect, while pitching for abandoning America's NATO commitments, had called the alliance "obsolete"
Earlier this month, Sweden announced it was remilitarising its biggest island, Gotland
NATO will hold fresh talks with Russia on July 13 in Brussels just days after the landmark alliance summit
Some of the allies however, especially France and Germany, have called for NATO to avoid a Cold-War style stand-off with Russia
US President Barack Obama announced his decision to send an additional 1,000 US troops to Poland as part of NATO efforts
Most of the NATO troops in Afghanistan are working as advisors to local Afghan security forces