"The leaders discussed how to encourage all NATO allies to meet their defense spending commitments," the readout of the talk released by the White House said, adding "continue close coordination and cooperation to address the full range of security challenges facing NATO."
The news comes as the Ukrainian forces resumed heavy shelling of the residential areas of Donetsk on Sunday, deploying additional troops closer to the borders of the self-proclaimed republics in the east of the country.
On Saturday, in a phone talk with Ukraine's President Poroshenko, Trump pledged to cooperate with leaders of Russia, Ukraine and other nations in order to restore peace in war-torn Donbass.
Recently, the situation in Donbass escalated with heavy fighting brewing in the vicinity of the industrial town of Avdiivka. Clashes are estimated to have left over 40 people dead and more than 100 wounded.
In February 2015, Kiev forces and Donbass independence supporters signed a peace agreement in the Belarusian capital of Minsk. The deal stipulates a full ceasefire, weapons withdrawal from the line of contact in Donbass, as well as constitutional reforms that would give a special status to the Donetsk and Lugansk People's Republics. Since then, the ceasefire regime has been regularly violated, with both sides accusing each other of multiple breaches, undermining the terms of the accord.
