A drive to impose more sanctions on Russia seems to be "gaining some traction" following a naval confrontation in the Black Sea last month, according to the U.S. special envoy for Ukraine.

Kurt Volker made the comments during an online briefing in Brussels on December 17, after Russian seized three Ukrainian Navy ships and 24 crewmen in the Kerch Strait that links the Black Sea with the Sea of Azov.

The November 25 incident escalated tensions in the region and prompted international calls for the sailors' release.

Russia has alleged that the vessels had illegally entered Russian territorial waters near the Crimea region, which Russia seized from Ukraine in March 2014.

Kyiv has accused Moscow of stepping up "aggression" against Ukraine.

Volker told reporters that in Europe, "the notion that there needs to be a response and some additional sanctions and listing of names would occur seems to be one that's gaining some traction."

"I would not be surprised at all to see that happen in the next month or two," he added.

Volker said the restrictions could have a "deterrent effect" on Moscow because "it will be an indicator to Russia that future acts will also be met with sanctions."

The European Union, the United States, and other countries have imposed sanctions on Russia over Moscow's seizure of Crimea and its support for separatists in a conflict that has killed more than 10,300 people in eastern Ukraine since April 2014.

Volker also said that keeping a multinational, visible presence in and around Ukraine, whether it was in the Black Sea or in parts of Ukraine that are relatively safe, could be "an additional step because it would raise the visibility of Russia's actions compared to what we now see."

NATO has pledged support for Ukraine's navy to improve its naval capabilities and the alliance said it will also deliver secure communications equipment to Ukraine's military by the end of this year.

Volker said a foreign military-financing package of around $250 million to sell additional military equipment to Ukraine was currently being reviewed by the U.S. Congress.