President Volodymyr Zelenskiy said Ukraine’s armed forces were capable of repelling any Russian invasion on Monday, as the country celebrated National Army Day with a display of US armored vehicles and patrol boats.

US Vice President Joe Biden has promised his “unwavering support” for Ukraine in its standoff with Russia, and will meet with Russian President Vladimir Putin on Tuesday to attempt to ease the conflict.

Ukraine has accused Russia of amassing tens of thousands of troops along its border in preparation for a large-scale military operation, heightening the threat of outright conflict between the two nations.

“The personnel of Ukraine’s Armed Forces continue to fulfill their most essential job – to protect the state’s freedom and sovereignty against the Russian aggressor,” Zelenskiy said in a statement.

“The Ukrainian army… is confident in its strength and capable of thwarting any hostile takeover ambitions,” he stated.

Russia has rejected speculation of a fresh attack on Ukraine as unfounded and provocative, but has warned the West not to violate its “red lines” and to prevent NATO’s eastward advance.

Zelenskiy will drive east to Kharkiv, a historic center for Ukrainian weapon manufacturing, to witness the arrival of tanks, armored personal carriers, and armored vehicles manufactured at the city’s facilities.

He will also travel to the Donetsk area, where the Ukrainian army is fighting Russian-backed rebels in a simmering conflict that Kiev claims has killed 14,000 people since 2014.

Several towns in Ukraine are commemorating the 30th anniversary of the establishment of an autonomous military following Ukraine’s independence from the Soviet Union in 1991.

Humvees built in the United States will be shown in Kiev, Lviv, and Odessa, Ukraine’s southern port city. There will also be a ceremony in Odessa to hand over two newly arrived US Coast Guard patrol vessels to Ukraine’s navy.

Ukraine has pushed NATO to expedite its membership into the military alliance, claiming that Moscow has no veto power. NATO’s leadership has expressed support, but has stated that Ukraine must first implement defense reforms and combat corruption.