WASHINGTON (AFP) - United States President Donald Trump has "deep concern" over Russia's armed seizure of three Ukrainian ships, the White House said on Wednesday (Nov 28) as Mr Trump decides whether to cancel planned talks with Russian President Vladimir Putin.

During a phone call between Mr Trump and his Turkish counterpart Recep Tayyip Erdogan, "the two leaders expressed deep concern about the incident in the Kerch Strait and the continued detainment of Ukraine's vessels and crew members", White House spokeswoman Sarah Sanders said.

Russian border patrol boats fired on, boarded and seized the three Ukrainian vessels, along with 24 sailors, on Sunday off the coast of Crimea, a Ukrainian region annexed by Moscow.

The clash has refocused international attention on the long festering conflict in Ukraine, a former Soviet republic where Russia has supported insurgents in the east and taken complete control of Crimea in the south.

Mr Trump said on Tuesday that as a result of the crisis, he is reconsidering plans for one-on-one talks with Mr Putin during the Group of 20 (G-20) meeting in Buenos Aires at the end of this week. Mr Trump and Mr Erdogan will discuss the issue at their own talks during the G-20, the White House said.

Meanwhile, Mr Putin defended Russian forces' actions on Wednesday, accusing the Ukrainians of having staged a "provocation".

Ukrainian President Petro Poroshenko accuses the Kremlin of preparing for "full-scale war".

Western governments have rallied behind Kiev, accusing Russia of illegally blocking access to the Sea of Azov, used by both countries, and of using force without justification.