An unarmed U.S. Air Force plane with American and worldwide observers flew a special flight over Ukraine Thursday in a show of solidarity after Russia's Ukraine naval confrontation last month.
The military added that "Russia's unprovoked attack" on Ukrainian ships near the Kerch Strait on November 25 is "a unsafe escalation in a pattern of increasingly provocative and threatening activity".
Pahon said the plane that was flown over Ukraine on Thursday was an OC-135 observation aircraft with U.S., Canadian, German, French, British, Romanian and Ukrainian observers aboard.
"The timing of this flight is meant to reaffirm USA commitment to Ukraine and other partner nations", Pentagon spokesman Eric Pahon told CNN.
Russian President Vladimir Putin, while commenting on the naval incident that led to the detention of Ukrainian ships in the Kerch Strait, noted the attempt to breach the maritime border was a provocation prepared in advance as a pretext to introduce martial law in Ukraine.
The treaty "promotes openness and transparency in military activities through reciprocal, unarmed observation flights", Pahon said.
As UNIAN reported, three Ukrainian vessels were captured on November 25 by Russian forces at sea near the Kerch Strait, which is the only outlet to the Sea of Azov and controls access to two major Ukrainian ports.
The United States is required to notify Turkey about the passage of vessels through the Kerch Strait under the 1936 Montreux Convention, CNN said.