"Your support for the sovereignty and territorial integrity of Ukraine, as well as your efforts to increase energy diversification, advance our shared goal to enhance European and regional security," Trump wrote in a Feb. 8 letter posted on the website of the U.S. embassy in Vilnius, Reuters reported Friday.

Read alsoRussia "testing ground" with Trump administration by escalating hostilities in Donbas – MEP GahlerAs reported earlier, the Kremlin said on Thursday it was unlikely that the situation in eastern Ukraine, where pro-Russian separatists are ranged against the Ukrainian army, would be part of any deal with U.S. President Donald Trump.