Billionaire oligarch Petro Poroshenko is likely to win Ukraine's presidential election on Sunday, but has told CNBC in an exclusive interview that Russia might not accept the results.
"Russia is absolutely unpredictable," Poroshenko replied, when asked if Russia would recognize the outcome of the vote.
Sunday's national election comes at a time of economic and political turmoil in Ukraine, which has been ongoing since pro-Russian president Viktor Yanukovych was overthrown in February. In early March, Russia annexed Crimea in the south of the country and since then, fighting has continued in Ukraine between pro-Russian separatists and Ukrainian forces.
The U.S. and Europe have responded to Russia's aggression towards Ukraine with an escalating series of sanctions. These include visa bans and asset freezes on companies and officials with links to President Vladimir Putin.
"No one could have predicted the aggression on Crimea," said Poroshenko. "Even having such a high price, with sanctions, depression in the economy, devaluation of the national currency, really strong problems in the future with the energy policy of Russia, even in that situation, Russia went off and made the aggression on Crimea."
Pro-West Poroshenko is known as the "chocolate king" in Ukraine, due to his confectionery business interests. He is seen far ahead in the polls, with a survey by market research group GfK indicating that around two-fifths of Ukrainians will vote for him.
Rival candidates, including former prime minister Julia Tymoshenko and former vice prime minster Serhiy Tihipko, are seen lagging, with less than 10 percent of the vote each.
Poroshenko told CNBC he would quickly end the conflict with Russia should he win the election, and would use the "right force" against pro-Russian insurgents in Ukraine.
"I'm sure we will stop the war in a very short period of time. We will find a way to establish a dialogue with Russia and I am absolutely sure we will not compromise on two issues: Crimean security and the European aspirations of the Ukrainian people," he said.
Poroshenko said his treatment of pro-Russian rebels would vary according to their level of violence.
"For the ones that do not kill people, we propose an amnesty—take their weapons and go," Poroshenko said. "For those who are fighting against Ukraine, who are killing us, we will want to use the right force."
Rival slams oligarchs
Meanwhile, Olga Bogomolets, who is also running in the presidential poll, said Ukraine needed a president, "not an oligarch."
"When you have oligarchs in power they are always splitting the country, always trying to show to each other who is more powerful," she told CNBC.
She dismissed polls indicating that Poroshenko was in line for a landslide victory, saying: "Who knows who will win? Sometimes the polls don't give the correct information."
Bogomolets is a doctor who was thrust into the spotlight after she provided medical care to protesters on Kiev's Independence Square. She insisted that if a powerful business figure was elected president, Ukraine would move backwards.
"Instead of developing as a democratic country with a middle class... we will again have 5 percent of oligarchs and 95 percent of people who are really poor," she added.