US President Donald Trump's administration is open to "virtually any mechanism" that will lead to a settlement of the conflict in Ukraine, said US Secretary of State Marco Rubio on Thursday.

"Trump is open to any mechanism that leads to a just peace in the war between Russia and Ukraine," Rubio declared during a press conference with NATO chief Mark Rutte in Antalya, Turkey ahead of the negotiations between the war-torn parties in Istanbul.

Rubio further emphasized that a military resolution wasn't feasible for the Russia-Ukraine situation and mentioned that "we want to see progress made in the next couple of days."