The United States says it will provide an additional $10 million in military financing to Ukraine to help bolster its navy after Russia captured three of Kyiv's ships at sea in late November.
The U.S. action announced by the State Department on December 21 came as Britain also set plans to provide assistance to Ukraine's naval forces following the November 25 attack by Russia in the Kerch Strait that links the Black Sea with the Sea of Azov.
Russia also arrested 24 Ukrainian sailors in the incident after its coast guard opened fire on the Ukrainian ships.
Moscow alleged that the vessels had illegally entered Russian territorial waters near the Crimea region, which Russia occupied and annexed from Ukraine in 2014. Ukraine and most UN member states do not recognize the annexation.
Under a 2003 treaty, Russia and Ukraine agreed to share access to the Sea of Azov. However, since the 2014 annexation, and the completion of the Kerch bridge earlier this year, Russia has slowly restricted access for Ukrainian ships.
The State Department said Washington "calls on Russia to immediately return to Ukraine the seized vessels and detained Ukrainian crews, to keep the Kerch Strait and the Sea of Azov open to ships transiting to and from Ukrainian ports, and to respect Ukraine's sovereignty and territorial integrity."
It said the aid was subject to approval in Congress, where Ukraine has wide support in its dispute with Russia. It added that it was taking the action in "solidarity with Lithuania and the United Kingdom."
Earlier on December 21, Britain and Ukraine announced that London would send instructors to assist in the training of Ukrainian marines.
“In January, a group of British Navy officers will come to Ukraine to organize interaction, to plan joint drills, and to determine what kind of logistic assistance the Ukrainian armed forces and the navy in particular may need,” Ukrainian Defense Minister Stepan Poltorak said following a meeting in Odesa with U.K. Defense Secretary Gavin Williamson.
Lithuania in early December said it was sending additional ammunition and more military and cybersecurity instructors to Ukraine as it condemned Russia's actions. The Baltic country has more than 20 instructors currently in Ukraine.
On December 13, NATO also pledged support for Ukraine's navy and said it would deliver secure communications equipment to Kyiv's military by the end of this year.
"Russia must immediately release the sailors and ships they seized and allow freedom of navigation including free access to Ukrainian port in the Sea of Azov," NATO chief Jens Stoltenberg told Ukrainian President Petro Poroshenko in Brussels.