Russian President Vladimir Putin has "lost Ukraine for good" with his move to annex Crimea, former prime minister Yulia Tymoshenko said on Friday in her first live television appearance since returning to Ukraine.
Tymoshenko, who spent three years in jail on what she said were politically motivated charges before being freed last month, appealed to fellow Ukrainians to be ready to fight in the event of a Russian invasion.
"Putin has lost Ukraine forever after declaring war on us," said the leader of the 2004 pro-Western Orange Revolution as she appeared on a live talk show in her trademark blonde plaited hairdo.
"Putin is Ukraine's enemy number one who seized our land with weapons... We must be ready for Putin to cross the red line," she added, saying around 100,000 Russian troops were massed on the Ukrainian border.
Kiev has expressed fears Moscow may venture into eastern Ukraine, home to a large Russian-speaking population, after seizing the Crimean peninsula.
But Tymoshenko insisted any such attempt would not succeed, saying Putin was "not the first dictator to behave in a fascist manner" and risked going the same way as other "deposed dictators".
The forceful 53-year-old was jailed after losing to Viktor Yanukovych by a razor-thin margin in a 2010 presidential poll.
Tymoshenko walked free on February 23 having served three years of a seven-year sentence for abuse of power, a charge she has always denied.
She left Kiev shortly afterwards for Germany, where she remained until this week, receiving treatment for severe back pain that forced her to use a wheelchair.
A telegenic but steely figure, she is closely associated with the corrupt and tumultuous years that followed the collapse of Soviet rule in the 1990s, dogged by suspicions of personal enrichment and opportunism.