Zelensky in his defiant morning video address said, "We don't care what army you have, we only care about our land… We will fight for it until the end."
Calling upon Russia's invasion in Ukraine in the early hours of February 24 he vowed Ukraine "will not try to find an understanding with terrorists".
The president of the war struck nation said, "For us Ukraine is the whole of Ukraine. All 25 regions, without any concession or compromise."
On Wednesday, the US is set to announce $3 billion in fresh military aid to Kyiv on the date it severed ties with the Soviet Union in 1991.
These funds from America are to help Kyiv in acquiring more weaponry, ammunition and other supplies for its armed forces.
Ukraine is head to head with Russian troops on its east and south borders with neither side advancing significantly in weeks.
The White House announcement comes as Washington warned Moscow could be planning a surge in strikes on civilian targets coinciding with Independence Day observations.
With gatherings been banned in the capital Kyivl instead of cheering citizens, Ukraine's Independence Day witnessed air raid sirens sounded in the morning.
Zelensky has urged citizens to be on guard against "Russian terror".
Ukraine not gaining on front but on global support
As the war entered its seventh month with no end in sight, British Prime Minister Boris Johnson pledged unlimited assistance to Ukraine.
Soon to be replaced British PM Boris Johnson said in a video message on Wednesday morning. “People are fighting with steel, with courage to defend their homes and their families, and to preserve their right to decide their own destiny in their own country."
He added, "However long it takes, the United Kingdom will stand with Ukraine and provide every possible military, economic and humanitarian support."
On Tuesday, German Chancellor Olaf Scholz warned Russia against further attempts to annex Ukrainian territory in the same way it did the Crimean peninsula in 2014.
Polish President Andrzej Duda also advised against any "appeasement", saying: "There is no return to business as usual in relations with Russia."
And French President Emmanuel Macron vowed European Union support for Ukraine would continue "for the long term".
Amidst these messages of support and solidarity, there was an absurd message on Wednesday from the authoritarian leader of Belarus who congratulated Ukraine on its Independence Day.
Belarus had offered its territory as a staging ground for Russia's invasion.
"I am convinced that today's contradictions will not be able to destroy the centuries-old foundation of sincere good neighbourly ties between the peoples of our two countries," Alexander Lukashenko said in a statement.
After half year of war
In the early days and weeks of Russia's invasion, Kyiv was under siege by Russian troops and the troops reached the suburbs of the capital.
Moscow's offensive quickly faltered, and its forces withdrew in late March to regroup for assaults on Ukraine's east and south.
But in the capital, Ukrainians were sombre about the anniversary after a half-year of death and destruction.
"Six months, the peace of life has been broken in every family," Nina Mikhailovna, an 80-year-old pensioner, said at Independence Square in central Kyiv, on Tuesday.
"How much destruction, how many dead, how can we relate to it?" she asked.
Kyiv's city administration said it would shut public service centres on Wednesday and Thursday, and shopping malls said they would close for the anniversary for safety concerns.
With inputs from AFP.
