Ukraine has warned that Russia has "almost completed" its build-up of forces that could be used for an offensive against the country, compounding fears that Moscow could launch an invasion at any time.

According to the Ukrainian Defense Ministry's latest intelligence assessment -- shared exclusively Tuesday with CNN -- Russia has now deployed more than 127,000 troops in the region.

"The full strength of RF AF (Russian Federation's Armed Forces) land group at the Ukrainian direction -- (is) over 106,000 personnel. Together with the sea and air component, the total number of personnel is over 127,000 servicemen," the assessment said.

The assessment called the situation "difficult," and said Ukraine believes Russia is "trying to split and weaken the European Union and NATO."