Ukraine's military intelligence said last week that Russia had more than 92,000 troops massed around Ukraine's borders and was preparing for an attack by the end of January or beginning of February.
Russia's foreign intelligence chief said on Saturday that such suggestions were "malicious US propaganda".
But Ukrainian forces who control the borders are prepared for any escalation between the two sides.
"If there is an attack, we have means for defence. We are well-prepared. We're getting ready, better day by day, considering different options. We can repel an attack without big problems and we're not afraid of it," said Oleksander.
Ukraine, which wants to join the NATO military alliance, has blamed Moscow for supporting separatists in a conflict in its east since 2014.
Russia has said it suspects Ukraine of wanting to recapture separatist-controlled territory by force. President Volodymyr Zelenskiy said on Friday that Kyiv had no such plans and Russia's rhetoric opposing Ukraine's bid to join NATO was worrying.
Ukraine received a large consignment of US ammunition and Javelin missiles earlier this year and soldiers say they also have mortars and Turkish attack drones.
"It's a bad idea to be afraid when someone comes to your house and you hide in your basement. It won't work. One should get up and go to fight," another soldier Vlad said.
"We're fighting here to not let them come, and then it's luck of a draw."