Marco Rubio (Photo by SHAWN THEW / EPA)

NATO Secretary General Mark Rutte held his first phone call with newly appointed U.S. Secretary of State Marco Rubio.

"Good call from Davos with new Secretary of State Rubio — great to have you on board! Looking forward to welcoming you to NATO and working together on Ukraine, Russia, China," Rutte wrote.

Rutte noted that increased defense spending in Europe and transatlantic defense production "makes us all stronger."

The day before, Rubio stated that he could not outline a timeline for ending Russia's war against Ukraine but believed each side would have to make concessions.