It comes as nations, especially in Eastern Europe, are lobbying the United States to increase the number of troops on the continent as they worry about combating an increasingly aggressive Russian Federation. Such an approach could allow joint training, but end the practice of having over-burdened US taxpayers foot the bill for wealthy Europeans' security.
The Washington Post recently reported that the Pentagon was evaluating the cost of transferring or withdrawing the troops - the biggest contingent outside the United States.
Following the summit, Trump will head to Britain, and on to Helsinki for a closely-watched face-to-face with his Russian counterpart Vladimir Putin.
Trump has expressed scorn for the alliance and is expected to upbraid European NATO members for not spending enough on their own defense.
"There is element of uncertainty in all this", said Nordenman, now the director of the Transatlantic Security Initiative at the Scowcroft Center for Strategy and Security at the Atlantic Council. Trump hasn't ruled out recognizing Russia's seizure of Crimea and suggested the USA has too many troops in Germany. He referred to Chancellor Angela Merkel, saying: "And I said, 'You know, Angela, I can't guarantee it, but we're protecting you and it means a lot more to you than protecting us 'cause I don't know how much protection we get by protecting you".
Congress is likely to oppose troop withdrawals and could pass legislation to prevent Trump from using money to move the military. Previously, Putin and Trump have had meetings on the margins of other global gatherings. Trump also rejected the joint communique signed by leaders at the conclusion of the meeting, launching personal attacks against Canadian Prime Minister Justin Trudeau in the process.
Also in the teleconference, Kay Bailey Hutchison, the USA envoy to the North Atlantic Treaty Organization (NATO), said Russian Federation would be a key topic at the NATO summit in Belgium next week.
The sanctions center on the financial, energy and defense sectors. They are strategically located to help in other regions of the world, such as counter Iran or strike the ISIS. All are former Soviet client states: Estonia, Latvia, Lithuania, Poland and Romania.
But Hutchinson, and the US ambassador to Russia Jon Huntsman, gave upbeat assessments of the upcoming meetings. That's in direct contradiction of NATO's pledge that an attack against one member is considered an attack against all of them.
Speaking of the possible topics of the upcoming meeting, Huntsman said "some of them might be around strategic stability and arms control".
The White House declined to say if and how Trump might punish the countries.